Gitlab shell problem

Our users are having issues pushing/pulling via SSH. I’ve checked the troubleshooting guide and rebuilt the authorized_keys file (but the supplied command didn’t work, I had to use ‘gitlab-rake gitlab:shell:setup’ for this to work) but no joy.

When I do a ‘ssh -Tvv’ it hangs at “debug2: shell request accepted on channel 0” and goes no further. There is nothing obvious in any logs I can see, it all looks fine, gitlab-shell.log just has the logs from rebuilding my keys file. I’ve found many references to similar issues but none of the solutions seem to work. Please help!

More info edit - I inherited this installation from another admin. I’m told it was installed using Gitlab CE downloaded from and besides this little issue all appears to be working fine.

Server detail
OS: CentOS 7.1.1503 (SELinux enabled - doesn’t appear to be the problem)
Gitlab: 7.12.0
Gitlab Shell: 2.6.3
Gitlab API: v3
Ruby: 2.1.6p336
Rails: 4.1.11

If any further information is required, just ask.