Hi Mac_Studio_User_WA_AU,
Having your Mac inputs working as expected is important. Have you tried restarting the Mac? Have you tried disconnecting and reconnecting the external display? Have you reached out to the display manufacturer for settings steps to correct the issue? Be sure to check if all inputs are present when the Mac is in Safe Mode. Follow the steps and article below for Safe Mode on your Mac.
- "On your Mac, choose Apple menu > Shut Down.
Wait for your Mac to shut down completely. A Mac is completely shut down when the screen is black and any lights (including in the Touch Bar) are off.
2.Press and hold the power button on your Mac until “Loading startup options” appears.
3.Select a volume.
4.Press and hold the Shift key, then click Continue in Safe Mode.
The computer restarts automatically. When the login window appears, you should see “Safe Boot” in the menu bar".
Start up your Mac in safe mode - Apple Support
Keep us updated on the progress.