Sorry to hear of the problems watching Sky Sports, we appreciate you taking the time to raise this with us via the forums.
Can you confirm if you are using the same log in details you use for your online account? You mentioned you select the Virgin Media logo like you always have done, have you been able to use this service previously? If so, when were you last able to access it?
Having checked, Sky Sports is still part of your package. If this is removed it will prevent you being able to log in and view the content via the app.
This may be something our IT guys need to look into. Before I send you a Private Message, can you log into TV Go and in the devices section there should be the option to for Sky and let me know what it says please? If you have reached the limit this may be causing the issues.