Best answer by Ken_Griffiths
Go into your Google Home App (main Home Page) and find the Sonos entry for the TV... it will be called something like “Sonos TV Control for Dining Room”, or similar, where 'Dining Room' is the Sonos Room Name for the Beam. It will have a TV icon to help you identify it.
You can either rename it to “TV” or give it the nickname of “TV” ... then try controlling the TV with “Hey Google Turn on my TV” etc.
Before renaming the device, please ensure you have no other devices called TV, otherwise you will be best giving it another name like “Sony TV” or “Samsung TV” etc. just as examples.
Hope that fixes your TV control.