I have also seen this error message happen at companies that have their own github repositories, but the developer is still trying to connect to "regular" github. For example, the company I work at (The Gap) has its own repository, which is here: github.gapinc.com. I am able to execute "ssh -T [email protected]" successfully and receive the message "You've successfully authenticated, but there's no ssh access." But I will always get "Permission denied (publickey)" if I try to execute "ssh -T [email protected]", because I shouldn't be using github.com. I should be using github.gapinc.com.