Hi
Believe me your far from alone with this problem !
I had the windows 10 now tv app on 5 devices and all of them gave me that message "oops......"
My login details were correct as i could login to my account on the now tv website.
Anyway i had to start using the now tv player and i could login on all my devices that way, although it took weeks as i had to delete my devices using windows 10 app and then had to wait until a new month started so i could swap devices to using the player.
Now i have swapped my devices to use the now tv player, i am getting the message "it appears your offline" and the player will not work.
Never had a problem with Netflix or Amazon Prime but Now Tv is just a lottery as to whether things work, whoever is in charge of their software needs to produce something that just works as i am a customer of now tv for 6 years but after my passes run out in a few weeks i am not bothering anymore with them.
