I’ve seen others successful in pairing the speakers as another ‘room’ in the software first, before then moving them to bonding them as surround speakers to the Beam.

That shouldn’t matter whether the connection is ARC or optical. You’d need to be sure the WiFi on the Beam  is not turned off, when set up as surrounds, those speakers switch from connecting to your WiFi signal to connecting to a signal from the Beam.

The ‘not connecting to ARC’ is a separate issue altogether. There are several possibilities, from the cable not being connected to the port on the TV that is labeled ARC, to a bad cable, to CEC, or whatever your TV manufacturer may have called it, not being turned on. I guess I should include the possibility that the TV doesn’t even support ARC itself. The community would probably need more details to give you more specific guidance. 

Thanks for your help. It’s seems I’ve resolved my issues after all. I already had the surrounds set up as a stereo pair. When I separated them and then created the link between the beam and the ‘ones’ it worked fine. Also the arc connection sprang into life. I think possibly I was trying to ‘connect’ when there was no output from the tv possibly? Also I have an Ethernet direct into the beam which was previously into a ‘connect’ which maybe confuses things. Thanks for the help and the quick response.