I just encountered this problem with my Apple TV (4th generation). After setting up a new account with DIRECTV, I was having trouble signing into many apps. I noticed was that the single sign-on in my settings did not seem to work with DIRECTV. This also did not work when I tried to sign-in through my provider through certain apps. The way I fixed this was to sign-in NOT ON MY APPLE TV but on my computer, tablet or phone. First, I had to go to my settings on my Apple TV and go to apps; then, click each individual app and select NEVER for the TV provider option. After that, I was able to sign-in on each app (unfortunately only 1 at a time) by going to each specific website the app provides to enter in the activation code. After you enter in the activation code, you will get redirected to sign-in with your cable provider, and then you can use that app. It is very annoying to have to do this for all apps that give you this problem but at least it works.