Chris Alemany🇺🇦🇨🇦🇪🇸just spent the better part of a whole day troubleshooting why an old Apple TV could connect to iCloud in May, but not today. Answer: Apple discontinued/deactivated Photo Stream in July, and that seems to have completely broken the iCloud Photo Sharing signin in AppleTV 7.1.2. (iTunes and Home Sharing still work)