What do you perhaps see if you toggle the status LED ‘ON/OFF/ON’ etc. in the main room (In Sonos App ‘Settings/System/SBeam room name]’) which you have bonded the Sub to? 
 

Also, what do you see if you toggle the Sub ‘OFF’ completely in ‘Settings/System/€Beam room name]/Sub Audio’ (toggle switch - top right corner of screen) above its volume-level slider bar?

Hello Ken,

On both cases, nothing changes on my sub gen3 LED light, always switched off the light.In addition, when I changed LED light into the room where I have added the sub gen3, LED lights changed from withe color to switched off in sonos beam and both sonos ones, but nothing happens with my sonos sub gen 3 LED light.

 

Please, could you help me here?

Thanks.

Regards.

I would first see what happens when you power off/on the Sub - leave it off for 30-40s and then power it on again - if the LED problem persists, after that then it maybe best to submit a system diagnostic report and note, or post, it’s reference back here and contact/chat with the Sonos Support Staff via this LINK and see if they can see any issues with the device.

Hello Ken,

Thanks for your help, finally I have submitted the sonos sub for revision after being talking with support team.

Thanks.

Regards.