Easiest fix is to clear the Teams cache on the roaming profile of the user.
Instructions taken from this websites and others: How to Fix Microsoft Teams Not Loading or Opening Issue (guidingtech.com)
- Go to %appdata%\Microsoft\Teams
- Delete everything in Application Cache > Cache
- Delete all files in: Blob_storage folder, Cache, Databases, GPUCache, IndexedDB, Local Storage and tmp folders
You do not have to clear the profile off every computer they have used.