After going around in circles and chasing my tale for an answer I finally figured out the solution to my particular issue. When I asked Alexa to turn on/off the Tv, the response was always, " Tv does not support that". Long story short, opened Alexa app on my tablet, found my Tv ("Sony Bravia") and Alexa suggested different comands to try, for example. "Alexa turn on/off (LIVING ROOM TV"). Alexa mute (LIVING ROOM TV") It turns out just saying turn on tv, turn off tv is confusing to Alexa as it needs to know what you labeled your Tv, for example. Living room Tv, Kitchen Tv, Bedroom Tv and so on. Once I told Alexa were the tv was assigned she executed the command and made me a sane person again. Hope this helps.
P.S. I love my Sonos, wow wee, thats some system.