Windows Notification Service (WNS) is not Reachable

Windows Notification Service (WNS) is not Reachable

We are seeing the error message below in Desktop Central under MDM / Enrollment.  Anyone know what this is?  Did not see this before today.  Maybe a port that needs to be opened?

Windows Notification Service(WNS) is not Reachable!   
Desktop Central is not able to reach WNS, Contact Support with the server logs.

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