If your iPhone 12 screen is not working, there are several troubleshooting steps you can take to try and resolve the issue:
Force Restart: Press and quickly release the Volume Up button, then press and quickly release the Volume Down button. Finally, press and hold the Side button until the Apple logo appears.
Check for Updates: Make sure your iPhone is running the latest version of iOS. Go to Settings > General > Software Update to check for and install any available updates.
Check for Damage: Check the screen for any cracks or damage. If the screen is damaged, it may need to be replaced.
Check Display Settings: Go to Settings > Display & Brightness and adjust the display settings to see if that resolves the issue.
Restore iPhone: If none of the above steps work, try restoring your iPhone using iTunes or Finder.
If none of these steps resolve the issue, it's best to contact Apple Support or take your iPhone to an authorized repair center for further assistance.