Cannot receive FaceTime calls

Check that FaceTime is actually turned on. Go to Settings > FaceTime and make sure the toggle is on and that your phone number or Apple ID is checked under “You can be reached at.” If that’s off or not selected, people won’t be able to call you.

Also try signing out of FaceTime in that same menu and signing back in, then restart the phone. A quick network reset (Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings) can fix it too if it’s a connection issue.