I have received the following error multiple times:
Could not read remote repository. Please make sure you have the correct access rights and the repo
Assuming you have done the proper SSH keys configuration according to github's instructions it might be a problem of pull with https and later pushing with git+ssh
to make it more clear
if you have used https to pull
git pull https://github.com/user/repo.git
then you have changed remote URL
git remote set-url origin git+ssh://github.com/user/repo.git
and tried to push after some changes and commits
git push origin master
you might get this error it happened to me
erase the local repository and re-clone using git+ssh
git pull git+ssh://github.com/user/repo.git
and now your push should work