Your Mac is locked and it needs to talk to Apples server to unlock it. But the server is not answering. This could be because of bad internet, server problem, or software glitch. You can try these things to fix it:
- Connect to good Wi-Fi and restart your Mac.
- Go to this website (https://www.apple.com/support/systemstatus/) and see if the server is working.
- If you have another Apple device, go to Settings > [your name] > Find My > Devices and remove your Mac from there. Then try again.
- If nothing works, call Apple (https://support.apple.com/contact) and give them your Mac serial number and proof of purchase. They might be able to help you.