What TV? Did you configure the TV to use eARC/ARC? Did you re-run Setup on the Beam afterwards? Can it play music ok?

My tv is LG65UJ6520. I went to my tv setting and set it to HDMI ARC. I went also to my phone's sonos app and tried to re set-up  but it says 'ARC not connected'. I think it is still trying to connect with my previous system (my old tv)

On most TV's not all of the HDMI sockets are ARC capable. Is the HDMI cable going to your Beam plugged in to the right socket on your TV?

Yes it's plugged in. There is a dedicated ARC HDMI slot and it is plugged right into it.

Should I just factory re-set it?

Don’t Factory Reset yet because this usually creates a lot of extra work.

I recommend disconnecting all HDMI cables from the TV and powering down both units. Give them a few minutes without power, power up, make sure that the LG’s SIMPLINK is enabled then connect BEAM’s HDMI cable. The units should discover each other and work out the details. Now you can connect other HDMI’s to the TV. 

It’s more likely to be an issue with the TV than the Sonos.

To be clear, the Sonos knows nothing about “which” TV it is connected to. It’s just looking for a valid HDMI ARC signal coming through the cable.

Which raises the suggestion, you may want to reseat all of the HDMI cables between the two devices, just on the off hand chance they’re not fully making the connection. 

If you felt like rebooting something, the TV is the more likely candidate, although there’s no harm in rebooting the Sonos. Remember, in order to reboot the TV, you have to remove the plug from the wall, you can’t just use the remote to “power it down”, that only puts it into “idle state”, not a full reboot, which is what you’re trying to do.

You are correct Airgetlam. The tv is the culprit. I just found out the solution now. LG is different. Going to  Setting>Sound>HDMI ARC to turn it on is not enough. You have to go deep in the menus. Go to Setting>All Settings>Sound>SIMPLINK>HDMI-CEC and turn it on. It's like LG want to hide the switch to turn on the ARC . Now I'm enjoying Sonos. Thanks everyone!!!

Late to this discussion. I agree about the hiding of the on switch for LG.

moving my Beam 1 from LG to Samsung was much easier than the initial set up with LG. How you are expected to know to go to : Setting>All Settings>Sound>SIMPLINK>HDMI-CEC especially when the manual is useless( in my opinion) I don5 know.

Anyway, Glad you got there!

All manufacturers seem to be hiding things -- in the interest of appearing “simple”. “CEC” (Consumer Electronics Control) seems complicated, prompting many manufacturers to use private names for CEC. “SIMPLINK” makes me laugh.

Plus, there are very informal rules about communicating over CEC. CEC is glacially slow at about 417bps (yes, that’s four hundred seventeen bits per second) When CEC works, it’s great. When CEC fails, it’s always “we’ve never seen that before” -- it must be the other guy’s fault. One of my favorite fails is the middle of the night cable box update. After the update the cable company turns the cable box ON. While this seems convenient, the other system components assume that the customer wants to watch TV and the other boxes turn ON too. I make a point of lowering the Volume when I stop watching TV.

I also lower the volume on switching off.

But, purely so that the next time I use my Sonos, probably for music, I don’t get blasted!

I have my Sitting Room system on 40% volume limit.  Music I then play around 20-30 on the volume slider, while my LG TV has to be on 70-80. Mind you I do have the bass and treble both down very low, to help push up dialogue on TV. A mixture of failing ears and modern dramas!