Maybe the repository has been moved, or maybe you have an old repository that was checked out with username and password authentication, and you can’t push to it anymore because GitHub requires ssh authentication now. That was true in my case, since I was going back to work on code I hadn’t touched for a few years.
Although you could just re-check-out the repository, that is unnecessary, and can be annoying if you have changes that you want to push.
Changing the remote URL for a git repository is a simple thing to do, but it’s not necessarily obvious. It’s done using the “git remote” command.
To display the URL of the remote repository:
git remote get-url origin https://github.com/xangis/SigmaTizm
git remote set-url origin firstname.lastname@example.org:Xangis/Sigmatizm.git