Have you perhaps tried setting up the TV remote again in the Sonos App “Settings/System/SBeam Room Name]/Remote Control”? Also try toggling off/on the “use infrared” option.

Toggling “use infrared” had no effect on the problem.

When I attempted to re] set-up the remote, the first task is to press the “+ volume” button.  As I held the “+ volume” button, the Beam light rapidly blinked white but the Sonos app claimed that the Beam had not detected anything.

Have you tried new batteries, or does the remote setup and work better with the lights in the room switched off? Some bulbs/lights in a room (even light from the TV screen) can interfere with IR signals (er.. apparently?).

I’ve tried new batteries but to no effect.  As I mentioned, the remote controls the Beam just fine after power-cycling the Beam, so it seems unlikely that interference is a possible cause.

As a software engineer, I suspect there’s an issue in the Beam’s software/firmware...perhaps the Beam maintains an internal log that may offer some clue…?

You will need the Sonos Support Staff to look at your system diagnostic report(s) - just post their references back here in the thread. If no one responds here in the next 24 hours, then you can contact the Support Staff via this LINK 

The only other consideration is a factory reset, (if it’s not your only sonos product in the Household) but I would leave that as a very last resort. 

Hope you get it sorted soon.

System diagnostic report submitted.  Confirmation # 1435855860.

Anyone had a chance to examine the diagnostic report yet?

As some time has now passed, I would perhaps follow the link in my earlier post to contact/chat to the Support staff.

@tb1445 Does your TV have a Bluetooth setting that can be turned off?

I turned off Bluetooth on the TV.  Issue persists.  The remote is set for IR, and I verified using my cell phone camera that the remote is indeed transmitting an IR signal when I press the volume.  My beam-TV connection is via an optical adapter (Beam=HMDI out, TV=optical in).

Multiple phone calls with SONOS Support were of no help.  Low-bandwidth connection & foreign accents made understanding challenging, and the techs always kept re-reading the same troubleshooting flowchart from the beginning: have you changed the batteries?  Any interference?  And so on.  The tech on the final phone call told me I should reboot both Beam and TV every time I wanted to watch TV.  Umm....no.

I ended up switching to a HDMI (Beam) to HDMI/ARC (TV) connection* and enabling CEC on the TV (which Sony apparently calls Bravia Sync).  After a hard reboot of both Beam & TV, I've been able to control the Beam volume using the Sony remote for about 2 days.

The root cause, whatever it may be, is still there in case any SONOS engineers are interested.

* The original (problematic) connection was HDMI (Beam) to Optical (TV) via the adapter that came with the Beam.