While everything appears to be OK on your Exchange Server 2016, when scanning using GSX Monitor you discover an actual error stating that the Managed Availability reported the OWA Protocol health set as unhealthy.
This behavior is verified by Microsoft in Exchange 2016 CU4. The bug requires updating to CU5 to be resolved.
- Monitor 'OWADeepTestMonitor' is 'Unhealthy'.
- [OWA] The Managed Availability reported 'OWA.Protocol' health set as Unhealthy.
How to Solve the Issue
Exchange is the root cause of the problem. To fix it you need to upgrade Exchange Server 2016 to, at least, CU5.
Microsoft Engineers were able to verify the behavior in CU4 in multiple labs. The problem occurs as HMWorker is not able to handle 401 response. A bug referring to CU5 has been submitted for this behavior. After upgrading to CU5 the issue is resolved. This is an issue that was caught and fixed on O365, and rolled into the CU5 update.
Microsoft Related articles
- Microsoft Exchange CU5
- Troubleshooting OWA.Protocol Health Set
- Microsoft Social Technet - Resolution in CU5