I've got the same problem in my iPhone5, running IOS 7. The app doesn't seem to recognize my Verizon FIOS account any more, so can see any of the channels on WatchESPN. I wonder where the problem is, and if anyone has a fix for it.
On my iPhone 5
with iOS 7.0.4
Just downloaded Fios Mobile app. Version2.0.7359 Fips code 34_003 (NJ_Bergen County)
Started watching live TV on lots of Channels.
Signed in with My Verizon User id and password which I also use to sign in to all my VZ services.
Suggest you uninstall app.
Update IOS version on iPhone ?
Shut down iPhone COMPLETELY after update.
Keep us posted on how you solved your problem.