When attempting to clone a repository, this error indicates that the repository requested does not exist, or you do not have permission to access the repository. There are a few solutions to this error, depending on the cause.
Typos happen, and repository names are case-sensitive. If you try to clone
firstname.lastname@example.org:user/repo.git, but the repository is really named
User/Repo you will receive this error.
To avoid this case, always copy the clone URL given on the repository's page and paste it when you clone. Never type out the URL by hand.
To update the remote on an existing repository, see this guide.
If you are trying to clone a private repository but do not have permission to view the repository, you will receive this error. Ensure that your user has read access to the repository, either as the owner of the repository, as a collaborator on the repository, or as a member of a team which has read access to the repository.
You should also ensure that the SSH key you are using is attached to your GitHub user account. You can check this with
ssh -T email@example.com:
ssh -T firstname.lastname@example.org # Hi username! You've successfully authenticated, but GitHub does not # provide shell access.
If all else fails, make sure that the repository really exists. If you're trying to push to a repository that has not yet been created on GitHub, you'll get this error.