Hello,
From the sound of it, you are using MacOS, right?
So yes, you need to remove the account in KeyChain first. If it is not there at all, it can be removed already.
next, uninstall Teams, then go to the following folder
/Users/[your username]/Library/Application Support/Microsoft/Teams
Delete Teams folder. Restart the device.
Reinstall the app. See if it helps.