Update Troubleshooting.md

doc/install/Troubleshooting.md

@@ -28,3 +28,7 @@ The following is a list of common error messages and solutions:
 ###### `panic: runtime error: invalid memory address or nil pointer dereference`
  - This error can occur if you have manually manipulated the Mattermost database, typically with deletions. Mattermost is designed to serve as a searchable archive, and manual manipulation of the database elements compromises integrity and may prevent upgrade. 
  - **Solution:** Restore from database backup created prior to manual database updates, or reinstall the system.
+
+###### `Token request failed`
+ - This error can appear in the web browser after attempting to create a new team with GitLab SSO enabled
+ - **Solution:** Check that your SSL settings for the SSO provider match the `http://` or `https://` choice selected in `config.json` under `GitLabSettings`