Have you followed the instruction on the FAQ?

Just to add, I have both the Beam (gen2) and Arc working with Magic Remote (2019) and the later (2022) version.

In the LG device connector (or whatever WebOS calls it these days) under Bluetooth/Sound Bar devices you now need to search for Sonos as the Soundbar manufacturer and select that from the search results. I seem to recall the search is case sensitive, so try it lowercase and sentence case.

Once setup the ‘universal’ Magic remote will work fine, but note it’s not really necessary to use infrared if the connection is via HDMI, just use CEC control instead. 

I only use infrared with the Sonos Ray, but I can confirm the Magic remote will work with the Beam etc.

Thank you for the reply.  I’m not sure why but I have that set and still no volume control.  I have CEC / Simplink turned on.  Connected with HDMI-ARC.  I also have eArc support on.  I set up Sonos in universal remote like you showed in your post.  
 

well, if you have it working then I know it’s possible.  I can’t figure out why mine isn’t working.  Maybe I’ll disconnect everything and try again.  My Sonos app can control sound at least but not Magic Remote 

What happens if you switch infrared off in the Beam room settings ‘Settings/System/nBeam Room Name]’ does CEC control not work for you? - are you using the 1.4+ HDMI heac cable that came with your Beam or another cable? Is the Beam cabled to the TV’s HDMI-2 (Arc/eARC) port?

Thanks for the suggestions.  I tried turning IR off and still remote isn’t controlling volume.  I have CEC turned on.  I’m using the Sonos provided HDMI cable and it’s connected to HDMI-2 ARC.   
 

I really don’t want to connect to optic.  I may restore everything to factory settings and start over or maybe just have a 2nd remote for volume.   I’m a bit obsessed with getting it working though :-)

If the magic remote works for the LG TV with Simplink set to ‘ON’, then  it should work for any CEC-linked device aswell.. have you run through the Beams ‘TV Setup’ in its room settings? - Note you don’t need infrared universal settings whilst the TV is powered on as it will use CEC to control the volume. Its universal infrared connection is only useful if the TV is powered off or you use the TV’s optical connection instead of the HDMI connection.

So your magic remote should be working here with the TV without any kind of infrared option, that’s whilst your TV is powered on. 

Thank you!  I have run the TV set up but I wonder if I could totally reset and run it again?  2 additional clues I have are the iPhone Sonos app is not recognizing that Beam is plugged into ARC.  It says ARC not found.  I tried deleting and installing the app and still it gives the error.  Oddly, I can still control the volume and settings from the app even though it says Arc not found.  
 

The second clue is I did change the TV wifi to the one used by my phone and Beam.  Previously the TV had been on a 2nd wifi.  Makes me question if Beam needs to be completely restored and started over 

odd that app doesn’t recognize ARC and odd Magic Remote doesn’t control volume.  Seems maybe connected to a single problem?

The Sonos App ‘TV setup’ should recognise the HDMI-Arc connection - my ’initial’ thoughts are to see what happens when you change the HDMI cable between the TV and Beam, but first simply try powering everything ‘off’ and ‘on’ again and leave the devices off at the wall socket for at least 3 minutes.

I reset my Sonos Beam Gen 2 back to factory setting and also my LG OLED C1 TV back to factory settings.  Unplugged all HDMI and set up the TV then started new setting up Sonos Beam.  I then hooked up Beam to HDMI-Arc.  
 

The good news, everything now works!  Beam is playing sound great from LG TV and the Magic Remote can control volume.  

I have no clue what was messed up. Maybe unplugging the one other HDMI device?  Maybe reset of one or other?  Thank you to those who provided help!  I almost gave up 
 

I’m having  the exact same issue! LG OLED C1 tv and Beam 2 the Magic Remote will not work to control the volume. Geek squad has been here twice and even replaced my motherboard parts. Geek squad is coming back Friday and I will ask them to do a reset to factory settings. Are you still having issues?? 

Did you set Sonos as the Soundbar manufacturer in the LG WebOS ‘device connector’ or whatever that is called these days? - when I set it up on the LG C9 I had to search for Sonos and I recall it was case sensitive. Once added, the magic remote then worked, but if you have connected the Beam using HDMI-ARC/eARC and CEC (Simplink), then I wouldn’t bother with the IR setup, just use CEC control of the Beam instead.

Yes unfortunately we followed all of those steps and still not working. 

If CEC control isn’t working to adjust volume, then it might be your HDMI cable to the Beam (it needs to be HDMI 1.4+ with heac support: (non-active)) - or there might be a fault in either the TV hardware/software or the Beam itself.

I assume Simplink is enabled on the TV and the Beam is connected to the ARC/eARC port (HDMI-2)? …So what happens when you run the ‘TV Setup’ in the Beams ‘room’ settings in the Sonos App?

I have the same issue after few months of use. I have tried everything in this thread (and others), and only fix was to reset both LG C2 and Beam2. Sonos original hdmi caple in earc connection.
 

then everything was great for few weeks..and now volume adjustment disappeared again. Just like that. 
 

any further advise? Setting parameters again in both devices takes a lot of time.
thanks

Same here, it got worse. Now I have to reset every time I turn off the LG OLED C2 TV. I am beginning to hate sonos, this is clearly a sonos issue as other speakers work fine. 

I have the older LG C9 OLED TV and I’m not seeing the issue here, FWIW.

I found a solution, a silly one but works without resetting.

1. Unplug power cord
2. remove all hdmi cables from tv
3. put only earc cable back in tv
4. Power tv. Now volume adjustment works again
5. later on (next day) put other hdmi cables back on tv

still dont understand the core issue, but it works.

I have a beam 2 in bedroom with magic remote that works fine and dandy but the beam 2 downstairs with LG C2 and magic remote will not work after doing all the steps in this thread, how ridiculous I have to use an old unmagic remote to control the sound on a very expensive set up, I’m not sure if its Sonos or LG’s issue though.