This is driving me nuts. I have the new Apple TV. Everything about it works fine. I'm signed into iCloud and have successfully purchased movies, etc on the device. However, I am unable to sign in to iCloud in the Photos app. I have entered my username email and password correctly. Definitely - after all it's the same one for my iTunes account which is working on the same Apple TV. I have iCloud Photo Library working perfectly well on several iPhones and Macs in my house. When I launch the Photos app it prompts me to sign in to iCloud. No matter how certain I am that I am entering the credentials correctly, it just chucks me back to the sign in page and I can't progress pass it. This has been an issue from tvOS 9.1 to 9.2 to 9.3. Has anybody got any suggestions?