Was having the same problem. I didn't have anything from Github in my Keychain – the problem was with my Personal Access Token. I had left all of the checkboxes empty at first, but then re-signed in after checking all the checkboxes to allow for permissions to be granted through the token ... it worked right away after that!
[https://help.github.com/en/github/authenticating-to-github/creating-a-personal-access-token-for-the-command-line]
Definitely second viewing this link if you are having this issue.