How to reset git authentication?

I think this article may serve you better: Github OpenSSH asking for password for an https link

To unset the git config --system --unset credential.helper command, you can do type git config --system credential.helper store (maybe also with --global and --local flag)

It seems that your credential manager stored wrong authentication and reuses it. Reset it.

git config --system --unset credential.helper

More information:

Remove credentials from Git

GitLab remote: HTTP Basic: Access denied and fatal Authentication