BLinc,
 

Not too sure if this will work for you, but perhaps try this when you’ve finished playing music and want to switch back to the TV and it’s audio, maybe see if saying this instruction (below) to Alexa first of all, then allows you to go onto control the TV and it’s audio volume:

“Alexa, Set mode to TV on dSonos Room Name]” eg:  “Alexa, Set mode to TV on Dining Room”

Thanks Ken.  Tried that but I got a reply “mode” is not an available command.  It is very strange.  IT did work previously and all I did today was add a smart switch to the device list.   

Do you perhaps have any other TV-related ‘skills’ installed in the Amazon Alexa App?

What can cause confusion is having smart-home devices with the same name - for example if your Sonos HT Room is called Lounge (as an example) then make sure it’s uniquely named in the Alexa device list - you don’t want a smart-plug or a light etc; with the same name. Also check the Alexa device list for duplicate names. 
 

If all else fails you could try removing the Sonos Skill in the Alexa App (give it a minute or so) and then reinstall the ‘skill’ and see if that fixes things.

Thanks. No duplicate names. TV Room is the only name.  Plus, the Alexa app WILL control the Sonos Playbase if streaming music but when I tell Alexa to stop music and turn on the TV Alexa won’t control the TV volume BUT I can with the Sonos app.  Weird.  Worked fine this morning and for the last several years.  I can’t figure out what could have gone wrong.   I tried the disable skill piece with no luck

In that case try switching off/on the HDMI-CEC control on your TV - this will have a different name depending on the make of your TV.

Some examples are: 

• Samsung - Anynet+
• Sony - BRAVIA Link or BRAVIA Sync
• LG - SimpLink
• Sharp - Aquos Link
• Vizio- CEC
• Hitachi - HDMI-CEC
• AOC - E-link
• Pioneer - Kuro Link
• Toshiba - Regza Link or CE-Link
• Onkyo - RIHD (Remote Interactive over HDMI)
• Panasonic - VIERA Link or HDAVI Control or EZ-Sync
• Philips - EasyLink
• Mitsubishi - NetCommand for HDMI
• Runco International - RuncoLink
• Insignia - InLink
• JVC - CEC
• Magnavox - Fun-Link
• Sylvania - Fun-Link
• Sansui - EasyConnect

If switching HDMI-CEC ‘off’ and then ‘on’ again fixes the issue, you may have a device connected to one of your TV HDMI ports that also has HDMI-CEC control switched on and is perhaps trying to  steal focus away from your Sonos HT product.  You could test that by powering off those devices, or disabling CEC on them (or use a HDMI CEC-Less adapter - see below link).

https://www.amazon.com/Lindy-HDMI-Adapter-Female-41232/dp/B00DL48KVI