PLT-1572 Adding more info to the error message

doc/install/Administration.md

@@ -100,7 +100,7 @@ To upgrade GitLab Mattermost from the 0.7.1-beta release of Mattermost in GitLab
     - Please check that each step of [the procedure for upgrading Mattermost in GitLab 8.0 to GitLab 8.1 was completed](https://github.com/mattermost/platform/blob/master/doc/install/Upgrade-Guide.md#upgrading-mattermost-in-gitlab-80-to-gitlab-81-with-omnibus). Then check upgrades to successive major versions were completed using the procedure in the [Upgrade Guide](https://github.com/mattermost/platform/blob/master/doc/install/Upgrade-Guide.md#upgrading-mattermost-to-next-major-release).
 
 
-###### `We couldn't find the existing account`
+###### `We couldn't find the existing account ...`
   - This error appears when a user attempts to sign in using a single-sign-on option with an account that was not created using that single-sign-on option. For example, if a user creates Account A using email sign-up, then attempts to sign-in using GitLab SSO, the error appears since Account A was not created using GitLab SSO. 
   - **Solution:** 
     - If you're switching from email auth to GitLab SSO, and you're getting this issue on an admin account, consider deactivating your email-based account, then creating a new account with System Admin privileges using GitLab SSO. Specifically: