Unable login to Skype for Business Mac and Mobile app

Error shows in SfB logs: HttpHeader:X-Ms-diagnostics 28042;source=”<Front-End FQDN>”;reason=”Too many outstanding requests for a single user.”

Why this happens?

Batch requests can contain any UCWA request, other than another batch request, photo request or event channel request.

UCWA limits the number of outstanding requests for each user, and if a batch request causes this limit to be exceeded, the request will be rejected with error code 429 / Too Many Requests.

In this case none of the requests in the batch is executed, so it is safe for a client application to retry the request later, preferably splitting it into multiple batch requests of smaller sizes.

The server-side limit in this version is set at 100 requests for a single user across all batches; a single batch with more than 100 requests can also exceed this limit. It is recommended that clients do not take a dependency on this specific number, as it can be changed in later releases. Instead, clients should split large batch requests into smaller ones if they encounter this error message and introduce a timeout between retries.

Resolution:

Restarting the services on affected servers will help to reset request count and that ultimately fixes the SfB Mac and mobile client sign-in.

Finally, ask affected users to sign-in to Skype for Business and they will be able to login to Skype for Business on Mac and Skype Mobile devices.

Thank you.