Are you signing in with a personal Microsoft account into some organization tenant?
If so, what's your current Teams app version number? You might need to see if you have update available shown on the upper right in Teams app, if so, update it and the issue should resolve itself.
If not, go to Teams app settings > Teams Insider program, if you are in the Insider program, you would see the "leave Insider" option. Do that. And see if that triggers the update to show up on the upper right.