I have had a surprising event with a fully functional 20.2.3 DaVinci install on Mac mini M4pro (sequoia ) that suddenly did not want to launch , so thinking of corruption I updated TO 20.3 same problem… I realized one of my media drive used in a project was off line and that was the culprit !
Usually loading DVR to project window showed projects with off line shots with red project but it seems this is a problem now.
Hope this could explain your situation?
This must be a bug, never had that happen since DVR v8