Hi, here is my set up.
LG CX OLED connected to the sonos arc SL from Costco via HDMI through the eARC port. Previously everything worked well until I had to unplug things today to mount the arc onto the wall.
After reconnecting I can no longer control the volume using the LG remote. I have tried the Philips method, setting up universal remote, reconnecting, powering off and trying different hdmi cables, trying to setup remote with the sonos app. Seems my issue isn't isolated after some research online but there is no consistent or reproducible fix.
I realized the following
1. The arc responds to the remote, blinking indicator light when the TV is turned off each time I press volume down.
2. The sonos app states my eARC is not connected, although I'm getting appropriate sound, my TV states it is using ARC out and eARC turned on.