Just like hundreds of other users, I haven't been able to use TV Go since Saturday. On any of the 3 devices I use (2 windows machines using Firefox as well as the Android app), the result is the same:
Oops, that hasn’t worked!
Please sign in with your main user account. Sub-accounts cannot sign in.
But, of course, I am using the main user account, which I can still use to log in to My Virgin Media. It's not a VM email address, in case that makes a difference. I can still use these credentials to log into Sky Sports, which streams perfectly, as does iPlayer in HD, and speed tests indicate the internet connection is perfectly good. I have updated the app, uninstalled & reinstalled it, no change.