Mattermost Needs Your Help
The service provider Openid did not provide an authorization code in the redirect URL.
For Google Apps make sure your administrator enabled the Google+ API.
For Entra ID make sure the administrator of your Microsoft organization has enabled the Mattermost app.
For GitLab please make sure you followed the setup instructions.
If you reviewed the above and are still having trouble with configuration, you may post in our Troubleshooting forum where we’ll be happy to help with issues during setup