Either way, we cannot answer your question because without any more details it’s impossible. Check the log files under /var/opt/gitlab and see if you can find out why. If you see any errors in the logs, post them. Otherwise it’s impossible for anyone to help you with such minimal information. Also check:
gitlab-ctl status
and make sure you don’t have issues with services not running, etc. Also would help to know exactly what version of Gitlab is installed and running.