Expert with dual band router

[Unclemonty]

Nick is correct.  Which Virgin Superhub do you have?
If you have a Superhub 2 it might be worth getting Virgin to upgrade it to a Superhub 2ac or Superhub 3.
I think there were some issues with 5GHz on the Superhub 2.

It's a Superhub 3 - quite new.  In fact tonight the app isn't working even with the 5ghz disabled.

Is there an advantage to setting a fixed IP address and might this resolve it? 

Thanks