$ git push -u origin master
ERROR: Repository not found.
fatal: The remote end hung up unexpectedly
I’m quite sure the repository is there and I added it correctly. The problem may be that I am using two github accounts. One is my personal one and one is for a client. I’m trying to get it on the client’s github as a private repository.
I am able to create a repository and push it to my personal github account. But I can’t get it to push to my client’s account.
You probably do not have permission to push to your client’s repository. To get access, the easiest way would be if your personal GitHub account had access to your client’s repository.
Ideally your client’s account is a GitHub Organisation. That way, an arbitrary number of people can be given permission to access its features. Just add any account as an owner of the organization, or add an account to a team to give access to specific repositories.
If your client’s account is not an organisation, you can give yourself access by adding your own account as a collaborator to the repository (in the repository admin settings). That gives you access to the repository from your own account.
If you are trying to use multiple ssh keys to login to different Github accounts depending on which repository you are pushing to, see Multiple GitHub Accounts & SSH Config. However, this is more difficult and is probably unnecessary.