Apple 12 call background is grayed out.

Do not disturb the mode or block unknown calls, mute the mode or turn down the volume.

1, Do Not Disturb Mode or Block Unknown Incoming Calls: When Do Not Disturb Mode is turned on or Block Unknown Incoming Calls is set, all incoming calls and short messages will be displayed in gray. You can check and turn this feature off in the settings.

2. Silent mode or volume reduction: When the phone is in silent mode or the volume is adjusted to the lowest, the call background will be displayed in gray. Try to adjust the phone's sound settings to make sure it's not mute.