More information please, several folks have looked at your post this morning and had no idea what you are asking for or how your system is set up.

I’ve attached/grouped 3 amps together.

 They will all play the main amps source via HDMI out of TV ARC connected to main amp, but when you raise or lower the main amps volume with the TV remote, the other 2 amps don’t follow the command.

 You can raise and lower volume thru the app on each independently, but not together when using the remote. 

TV remotes only control the volume of the attached Amp, they do not control any Group that may be attached to it.

I assumed it would work that way.

Thanks for the info