You can’t bond the amp (for sub) to the Arc + surround setup in the same ‘room’ as you would a Sonos sub or mini sub.  It’s not supported.  You obviously setup the amp as a 2nd room.  The TV volume will only control the volume of the Arc + surround room.  You would need to use the Sonos app, or some other 3rd party controller to control volume of a group, as your TV remote won’t do that.

In other words, this is a feature, not a problem to fix.

thank you Danny,

and as i understand, there was no issue, if the sonos would allow to add ARC to AMP like the SL can add? then you could connect tv and amp and controll all the system via amp.

K

You can bond the Arc with surround speakers and with a wireless sub (Sonos sub or sub mini).  The surround speakers can be Fives, Ones, etc or it can be an amp powering a pair of passive speakers.  However, when you use the amp for surround sound duty, you cannot connect a powered sub to it.

You also have the option of connecting the amp directly to the TV, where the amp is playing the front audio channels.  You can connect a powered sub or wireless sonos sub in this case.  You have the same options for surround sound.  You would not be able to use an Arc with this setup though, and thus would not have any atmos audio capabilities.