When SB scale-out has un-recoverable error ConfigurationErrorsException for SB connectionString, now it doesn’t throw (/signalr/hubs request returns 200) and will retry forever:

https://github.com/SignalR/SignalR/blob/release/src/Microsoft.AspNet.SignalR.ServiceBus/ServiceBusConnection.cs#L49

In 2.0.2, , ServiceBusConnection will throw exception (/signalr/hubs request returns 500) and will not retry forever for ConfigurationErrorsException