If anyone else has this problem, the solution is to change the login shell of the user ‘git’ (or whatever your user is called) to /bin/bash. This can be done via the command : usermod -s /bin/bash git (Link). The reason for changing the login shell is because the default shell for the git user is /sbin/nologin (or similar, depending on environment), which prevents the git application from logging in as the git user on the git server.