I have several Sonos AMPs that work perfectly fine on several TVs.   But this one TV is driving me crazy!   I have all the TV settings correct (or at least match my other working setups in the house).   It’s a slightly older Samsung TV (2015-2106), so that might be part of the problem, but when I turn the TV on there is no sound.   I have to go into the Sonos app and manually tell that room to play TV and then it works fine.  
 

Why do I have to manually select TV inside the Sonos app to make it work?  While it technically works, I can’t require guests and other family members go to an app to get sound.  Is it just an old TV with a less advanced version of ARC that isn’t auto detecting and sending?