So I have a single user out of 60 people in my company that has this issue. It's been happening for about a week now on and off. Here's the steps I've tried:
1) Had her change her O365 password
2) Uninstalled, rebooted, reinstalled. No difference
3) Uninstalled, ran CCleaner, manually deleted all registry entries for Teams, reinstalled. No difference
4) Had her sign on to a different computer, same problem occurred
5) Told her to use Teams through the website, same problem occurred.
6) I cleared the files/folders out of c:\users\username\Appdata\Roaming\Microsoft\Teams\
My user relies heavily on Teams and it doesn't work for her half of the time.
PC is running Win 10 Pro x64 v1803.
She hits discard now then gets about 15 seconds to 5 minutes of usability for Teams then the error pops up again.
Does the error message just pop up regardless what the user is doing or is it when she is performing any specific operation?