For no apparent reason, an InDesign file I had been working on in InDesign CC 2020 refused to output to PDF. After a force quit, that file (and others I’ve tried as well) would either not open, or would open but then freeze (spinning beach ball) if I tried to work within that file, change the workspace or anything else for that matter. I forced quit, uninstalled the CC 2020 version and then installed the CC 2021 version with still the same issues. I performed the opening of the app so that preferences would be discarded (shift + control + option + command) but still experiencing the same issues.
Photoshop 2021 opens with no issues. No Issues with Acrobat Pro DC. Illustrator is having the same issue as InDesign, where the app hangs up (spinning beach ball) when opening.
Other apps such as MS Office Word, Excel and PowerPoint open and function properly. Safari, Messages, Mail work fine.
I’ve closed all open apps and restarted my Mac several times. iMac (Retina 5K, 27-inch, 2017). Processor:
I've had major problems with InDesign 2020 and 2021 as well. For me they just either won't launch properly, or else they launch, then just hang up. After Force Quitting they will not re-launch unless I restart the computer. I finally have decided to just go back to InDesign 2019 (v14 something). One problem you may have is that if you're using Mojave, which is an older OS, it may not like 2021. If you can, upgrade to Catalina. Having said that though, I'm running Catalina and 2021 InDesign just really doesn't work properly. It's not worth the wasted time. Maybe revert to InDesign 2019?