The short answer is that the Virgin Connect app is a piece of junk and shouldn't be used. It hardly ever works.
What do you need the app for? If it's to find WiFi dead spots then you would be better of acquiring your own WiFi router which will give you far better WiFi than the hub 3, or you could get a full house WiFi kit.
Virgin also do whole house WiFi, but take notes of the charges compared to how much you can buy an equivalent system for (unless you are on one of the high end packages in which case they are normally free so worth checking out).