I deleted all my authenticated Accounts and Git Saved Passwords from Sourcetree.
Then I added my github account via OAuth. It loaded a browser window and gave a green checkmark indicating that it authenticated successfully (since I'm already logged into github in the browser). Then when I try to Fetch changes, it tells me username and password failed to authenticate.
WHY WOULD IT TELL ME IT AUTHENTICATED CORRECTLY AND THEN **NOT** AUTHENTICATE WHEN I TRY TO FETCH?!?!?!
This seems to happen once a month and I try a million combinations and orders of clicks to make it work.
PLEASE FIX THIS MAJOR ANNOYANCE!
I had this problem, or something which seems very similar.
It seemed to be resolved by revoking the Sourcetree authorization in App authorizations in Bitbucket and getting Sourcetree to request access once again.
Must be related to the order I did things trying to resolve the initial connectivity issues I had.