Update Troubleshooting.md

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/install/Troubleshooting.md b/doc/install/Troubleshooting.md
index 14b931ec6..78ab5617d 100644
--- a/doc/install/Troubleshooting.md
+++ b/doc/install/Troubleshooting.md
@@ -52,3 +52,15 @@ The following is a list of common error messages and 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. 
 
+###### `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: 
+       1. Deactivate your email-based System Admin account (note: this process is [scheduled to improve](https://mattermost.atlassian.net/browse/PLT-975))
+         1. Temporarily turn off email verification (**System Console** > **Email Settings** > **Require Email Verification** > **false**, or set `"RequireEmailVerification": false` in `config.json`).
+         2. Change email for account to random address so you can create a new GitLab SSO account using your regular address.
+       2. Create a new Mattermost account using GitLab SSO
+         1. With GitLab SSO enabled, go to `https://domain.com/teamname` and sign-up for a new Mattermost account using your GitLab SSO account with preferred email address.
+         2. [Upgrade the new account to System Admin privileges](https://github.com/mattermost/platform/blob/master/doc/install/Troubleshooting.md#lost-system-administrator-account).
+       3. Deactivate the previous System Admin account that used email authentication.
+         1. Using the new GitLab SSO System Admin account go to **System Console** > **[TEAMNAME]** > **Users**, find the previous account and set it to "Inactive"