This has only started occurring very recently.
Every time I try to pull down the latest from my Github repository, I keep being prompted to login to Github. The dialogue doesn't appear to accept my credentials (I confirmed they are correct, by logging into Github in my web browser) and continues to appear every 5 seconds or so.
I have tried removing my Github credentials from my Windows credential manager, as well as removing my Github account from SourceTree under the Authentication section of Options. I have also tried updating the embedded Git.
I am running SourceTree version 2.4.8. I also have 2FA setup on my Github account, if that helps. Let me know if I can provide any more information to get the support I need.