And, then, in the end... it didn't work. I was trying to teach a class, but my students couldn't see what I was doing. I had no idea why.

Were you on a mac?

If so, you may have encountered https://answers.microsoft.com/en-us/msoffice/forum/msoffice_... which has been outstanding since October and has no sign will be fixed properly any time soon.

The workaround is quit programs until you find the one that somehow causes Microsoft Teams to not understand that it really does have permissions. For me it seemed to be XCode. But it could be others...here is a partial list:

  - Harvest – Confirmed
  - Sonos – Confirmed
  - Cisco VPN – Issue reported by others
  - Microsoft To-Do – Confirmed
  - Contacts+ (formerly FullContact) – confirmed
  - Apple Photos – confirmed
  - Teamviewer – reported by others
  - Prompt/popup for app review from App Store – still have questions here. This seemed to be it, but haven’t been able to confirm
  - Brackets – reported by others
  - Citrix Workspace Version: 19.10.2.41 (1910) – confirmed

This is an example of why "just works" is so important.