bu şekilde çalıştırdığımda. Markalar geliyor fakat seçime göre modeller listelenmiyor nerede hata var ?

                    <div class="form-group row">
                      <label class="col-sm-2 col-form-label">Marka</label>
                      <div class="col-sm-10">
                        <select class="form-control" name="marka" id="marka">
                          <option value="">SEÇİNİZ</option>
                        </select>
                      </div>
                    </div>
                    <div class="form-group row">
                      <label class="col-sm-2 col-form-label">Model</label>
                      <div class="col-sm-10">
                        <select class="form-control" name="model" id="model" disabled="disabled">
                          <option value="">SEÇİNİZ</option>
                        </select>
                      </div>
                    </div>
<script src="https://code.jquery.com/jquery-1.12.4.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js"></script>
<script>
    $.getJSON("marka.json", function(sonuc){
        $.each(sonuc, function(index, value){
            var row="";
            row +='<option value="'+value.marka+'">'+value.marka+'</option>';
            $("#marka").append(row);
        })
    });
    $("#marka").on("change", function(){
        var marka=$(this).val();
        $("#model").attr("disabled", false).html("<option value=''>SEÇİNİZ</option>");
        $.getJSON("model.json", function(sonuc){
            $.each(sonuc, function(index, value){
                var row="";
                if(value.marka==marka)
                {
                    row +='<option value="'+value.model+'">'+value.model+'</option>';
                    $("#model").append(row);
                }
            });
        });
    });
</script>
marka.json
[
                {
                               "marka":"APPLE",
                               "kod": 1
                },
                {
                               "marka":"SAMSUNG",
                               "kod": 2
                },
                {
                               "marka":"LG",
                               "kod": 3
                },
                {
                               "marka":"OPPO",
                               "kod": 4
                }
]
model.json
[
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 5",
                               "id"        : 1,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 5s",
                               "id"        : 2,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 6",
                               "id"        : 3,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 6 plus",
                               "id"        : 4,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 6s",
                               "id"        : 5,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 6s plus",
                               "id"        : 6,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 7",
                               "id"        : 7,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 7 plus",
                               "id"        : 8,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 8",
                               "id"        : 9,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 8 plus",
                               "id"        : 10,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone XS",
                               "id"        : 11,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone XS Max",
                               "id"        : 12,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone X",
                               "id"        : 13,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone XR",
                               "id"        : 14,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 11",
                               "id"        : 15,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 11 Pro",
                               "id"        : 16,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone 11 Pro Max",
                               "id"        : 17,
                               "kod"    : 1
                },
                {
                               "marka"               : "APPLE",
                               "model"               : "Iphone SE",
                               "id"        : 18,
                               "kod"    : 1
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "S7",
                               "id"        : 19,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "S7 Edge",
                               "id"        : 20,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "A9",
                               "id"        : 21,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J1",
                               "id"        : 22,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J1 Mini",
                               "id"        : 23,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "A9 Pro",
                               "id"        : 24,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J3",
                               "id"        : 25,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J5",
                               "id"        : 26,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J7",
                               "id"        : 27,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "C7",
                               "id"        : 28,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "C5",
                               "id"        : 29,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J3 Pro",
                               "id"        : 30,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "S7 Active",
                               "id"        : 31,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "Note 7",
                               "id"        : 32,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J5 Prime",
                               "id"        : 33,
                               "kod"    : 2
                },
                {
                                "marka"               : "SAMSUNG",
                               "model"               : "J7 Prime",
                               "id"        : 34,
                               "kod"    : 2
                },{
                               "marka"               : "SAMSUNG",
                               "model"               : "A8",
                               "id"        : 35,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "C9 Pro",
                               "id"        : 36,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J2 Prime",
                               "id"        : 37,
                               "kod"    : 2
                },
                {
                               "marka"               : "SAMSUNG",
                               "model"               : "J1 Mini Prime",
                               "id"        : 38,
                               "kod"    : 2
                },
                {
                               "marka"               : "LG",
                               "model"               : "G6",
                               "id"        : 39,
                               "kod"    : 3
                },
                {
                               "marka"               : "LG",
                               "model"               : "G7",
                               "id"        : 40,
                               "kod"    : 3
                },
                {
                               "marka"               : "LG",
                               "model"               : "V30",
                               "id"        : 41,
                               "kod"    : 3
                },
                {
                               "marka"               : "OPPO",
                               "model"               : "RX17 Neo",
                               "id"        : 42,
                               "kod"    : 4
                },
]