Additional sign-in or account-related issues within Microsoft Teams for business
I had this issue on a new install of Teams on a new Mac Laptop today.
Saw the "loading Microsoft Teams" dialog and a second Teams window in the background which showed a menu bar, but a blank, all white main content frame where normally Teams would display it's chats etc.
Tried reinstalling Teams. No improvement.
Tried deleting the contents of the ~/Library/Application Support/Microsoft/Teams directory. No Improvement after re-entering the user login.
The Chrome version of Teams web client worked immediately.
The Safari version of the Teams web client failed until I changed Safari's Privacy settings, where I had to untick the "Prevent cross-site tracking", to get Teams web client to work.
For the Teams app, I had to delete the ~/Library/Application Support/Microsoft/Teams to cause a sign-out. Then log in as a different user (which worked), then sign out and in as the original intended user, which allowed Teams to retrieve the correct content.
Not a solution that is able to be resolved without help from colleagues or IT support.