Update Troubleshooting.md

doc/install/Troubleshooting.md

@@ -34,3 +34,7 @@ The following is a list of common error messages and solutions:
  - **Solutions:** 
    1. Check that your SSL settings for the SSO provider match the `http://` or `https://` choice selected in `config.json` under `GitLabSettings`
    2. Follow steps 1 to 3 of the manual [GitLab SSO configuration procedure](https://github.com/mattermost/platform/blob/master/doc/integrations/Single-Sign-On/Gitlab.md) to confirm your `Secret` and `Id` settings in `config.json` match your GitLab settings, and if they don't, manually update `config.json` to the correct settings and see if this clears the issue. 
+
+#### Troubleshooting GitLab Mattermost
+
+- If you're having issues installing GitLab Mattermost with GitLab Omnibus, as a first step please turn on logging by updating the [log settings](https://github.com/mattermost/platform/blob/master/doc/install/Configuration-Settings.md#log-file-settings) section in your `config.json` file installed by omnibus, and they try a general web search for the error message you receive.