Creating a Azure Service Bus Topic Subscription fails

Question

I have been instructed by the AzureSupport twitter account to create a post here about an Azure Service Bus issue I'm running into. (Original Twitter thread: https://twitter.com/heyimjacooob/status/940769610588086272 )

Basically all attempts to create a subscription for a Service Bus Topic fail. I have tried in Chrome, Safari and Firefox - all behave the same way. The creation bade validates successfully, and allows me to click the "Create" button - but after I am taken back to the previous blade it gives me the following message;

Answer 1

I was informed that this was a regression in the portal due to a recent deployment and it has since been fixed. A fix for all the regions would be rolled out as well. Sorry for the inconvenience.