Azure notification hub - unexpected exception when sending notification

Question

Resently the Azure Notification hub has started to fail when I try to send notification:

NotificationOutcome outcome = await m_hub.SendAppleNativeNotificationAsync(GetiOSPayload(head, body), tag);

I found similar reports and updated to .net 4.8 - but this has not solved the problem.
Does anybody has an idea what to do? ( I am able to send from Azure portal with same payload)
Thanks, Thoger

I get below exception:

at Microsoft.Azure.NotificationHubs.ExceptionsUtility.HandleUnexpectedException(Exception ex, String trackingId)
at Microsoft.Azure.NotificationHubs.NotificationHubClient.<SendRequestAsync>d__201.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Azure.NotificationHubs.NotificationHubClient.<>c__DisplayClass189_0.<<SendNotificationImplAsync>b__0>d.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Azure.NotificationHubs.NotificationHubRetryPolicy.<RunOperation>d__41.MoveNext() at Microsoft.Azure.NotificationHubs.NotificationHubRetryPolicy.<RunOperation>d__41.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at Microsoft.Azure.NotificationHubs.NotificationHubClient.<SendNotificationImplAsync>d__189.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at Visility.Webpoint.Respository.NotifyHub.<Notify>d__5.MoveNext() in E:\projects\VisilityNext\Visility.Webpoint\Respository\NotifyHub.cs:line 103