#git

Pushed to a repository I definitely had access to and was told I didn’t. The key was the problem: GitHub only lets a key be registered once across all accounts, and mine was still attached to the other one.

Nothing in the error says that. You get a message about the repository, so you go and check the repository, and everything there is fine.

ssh -T git@github.com

The reply names the account it just authenticated you as. When that’s the wrong name, stop looking at permissions.