Are you able to try Sky Sports to see if you get the same issue please?
If we take the iPad first to try an get that working then we will go back to the iPhone 6.
If you log into your TV Anywhere account (through a PC/laptop) on the right under My Profile select Sky Movies and Sky Sports. Find the iPad, remove the device from the list and un-install the app completely on the iPad. Re-install the Sky app on the iPad, sign in with your Virgin Media details and select a channel to stream for re-registration.