A user is repeatedly prompted for credentials in Outlook, and the authentication flow fails. In the Okta System Log, the following event appears:
Authentication of a user via Rich Client. Failure: Multiple users found in Okta.
- Office 365
- Federation
- Error
- Okta Classic Engine
More than one user is assigned the same application username to the Office 365 application in Okta.
When Outlook tries to connect to Office 365 through Okta using Basic Authentication, it cannot determine the user associated with the email account, as it sees more than one user assigned to the same application username in Okta.
Also, if a Windows user tries to access a Windows machine that is domain-joined with Entra ID, the system log shows the Authentication of a user via Rich Client. Failure: Multiple users are found in the Okta error as well.
Validate if more than one user shares the same username under the Assignments tab of the Office 365 application in Okta and update the application username of the affected user.
