Same problem here. Media Encoder became absolutely useless to me: Failed to start and crashed every time I tried to us it. Send a segment from Premiere — either to encode or cue. Crash, crash, crash. Tried restarting repeatedly. Nope. Tried deleting and reinstalling the app. Nope, again. Heck, I even tried deleting ALL CC apps through Cleaner and reinstalling them. Everything works except Media Encoder. Still crashed every time I tried it. So I tried deleting it again and going back one version. Same crash. Finally, after reading the post, above, I went back to 14.0.4. That’s a retreat FOUR versions back before I could get it to work. Adobe, when you did beta testing did you test out really, really hard things like, uh, trying to just friggin’ START the application?
MacPro Late 2013
Catalina OS up to date
All CC apps up to date
Very clean system
(So tell me why this is my fault…)