Message was not processed: Authentication Required (401) means:

• An invalid username and/or password was used in the request
• Contain the appropriate authentication type, such as basic authentication (username password) or SAML.

In the Gateway Audit Events, the Associated Logs should help you identify if the failure is due to some issue with Basic Authentication, SAML, or both. In this example, a bogus username was used in the request.

If the user forgot their password, you can reset the users password.