Okta Office 365 Rich Client Authentication Error "Multiple users found"
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Overview
Outlook repeatedly prompts a user for credentials, and the authentication flow fails because multiple users share the same application username. Update the affected user's application username to resolve the issue. In the Okta System Log, the following event appears:
Authentication of a user via Rich Client. Failure: Multiple users found in Okta.
Applies To
- Okta Classic Engine
- Okta Identity Engine (OIE)
- Office 365
- Federation
- Error
Cause
Multiple users share the same application username for the Office 365 application in Okta. When Outlook attempts to connect to Office 365 through Okta using Basic Authentication, Okta cannot determine the user associated with the email account because multiple users share the same application username. Additionally, if a Windows user attempts to access a Windows machine that is domain-joined with Microsoft Entra ID, the System Log displays the same error.
Solution
How does an administrator resolve the multiple users found error?
Validate the application assignments and update the application username of the affected user by following these steps.
- Navigate to the Assignments tab of the Office 365 application in the Okta Admin Console.
- Validate if more than one user shares the same username.
- Update the application username of the affected user to a unique value.
