Locating documents and sharing them with others within Microsoft Teams channels or chats
Hello,
A user in our environment is having the same issue. It has been about 4 days since the UPN was changed for the user and they are still receiving this error whenever they try to upload files in Teams messages.
This occurs on both the Teams client and Teams web, so it appears to be an issue with the account. We have tried all of the troubleshooting steps you described with no success.
Thank you.