When attempting to rent a movie on ATV, my wife received the error message above.  Alternately “server unavailable”.  When your wife is sick, the amount of IT support she needs goes up exponentially.  One piece of the puzzle was that she had changed her Apple ID password.  On her PC I ran iTunes and under account, there was only 1 device listed (not the ATV).  Even when signed out/back-in on the ATV under Settings>iTunes it still gave same error message. 

What I suspect is it thinks she is trying to authorize the device to another Apple ID.  Some new 90 day rule limits when a device can be associated with another Apple ID.  Your iTunes store/account will show devices, and how long before they can be associated with a different Apple ID from the Account Information page in iTunes on your computer.  Apple must have no freaking idea why someone would want to know which ID is associated to the ATV (i.e. the vice versa), because it can’t be done.

Solution:

1. Try ATV settings>reset
2. I swapped out ATV 1 for ATV 2 (used for music streaming downstairs).  I know it’s a cop-out solution, but remember I had a sick wife breathing down my neck.