[Solved] After GitLab Mattermost install nothing but logo is shown

I have noticed sometimes you need to run sudo gitlab-ctl reconfigure a 2nd time before mattermost gets installed correctly with the gitlab onmibus.

1. uncomment mattermost_external_url
2. run sudo gitlab-ctl reconfigure
3. Test mattermost site (may not be working)
4. run sudo gitlab-ctl reconfigure again
5. Test mattermost site again and it appaers