three options to resolve the issue :
- sign-out and sign back on in case this is related to last session caching
- Clear the folder [yourname]AppDataRoamingMicrosoftTeams …
- sign-out of team and close all task or apps in the control pannel.
- copy the content of the folder before deletion to a temp location for “undo” if needed.
- delete the content of the folder
- open team and wait for all cache folder to re-generated.
- test if sharing works
- within teams setting make sure your full screen is on