I had my notification client registered and was able to send notifications normally, suddenly, I tried again and I am getting this all the time (tried many times over 4 hours period):
Error code: GatewayTimeout
Message: The gateway did not receive a response from 'Microsoft.NotificationHubs' within the specified time period.
I tried to send from the portal, VS2k19, and the console, nothing has arrived.
What is the possible problem?