@CuthbertO Please provide some additional details as an error message or describe what doesn't work and I will try to assist.
Just for the sake of it. If not already done, try a removal and re-installation of the Teams app. You could also try deleting the Teams cache located here %AppData%\Microsoft\Teams\ (go to start, copy/paste and hit enter and delete the content in the Teams folder).
If on a Mac ~/Library/Application Support/Microsoft/Teams