My sub no longer works. I have removed from it and factory reset it 
but unfortunately no sound.  

I tested wiring the Sub directly to the Playbar via Ethernet cable and reset & configure it as you recommended but no sound from the sub.  The diagnostic confirmation # is: 1338909531.

The Sub works using an ad-hoc 5Ghz WiFi connection to the room it’s bonded with - so ensure the radio is switched ‘on’ in the Playbar room settings in the App, try toggling it ‘off’ and ‘on’ again.

Also try attaching the Sub to a different Sonos room (if you have one available) to see if it then works, if it does, then that may point to an issue (perhaps) that your 5Ghz wireless adapter isn’t working on the Playbar, rather than it being a Sub issue… it’s worth moving the Sub aswell to a different position and much nearer the playbar when testing the connection between the two units.

I Also try attaching the Sub to a different Sonos room (Play Base - Bedroom) and the Sub doesn’t  work, As you said. I  already have connected to the play bar two Play1 (Left & Right) and are working fine. I merge the play bar and Play Base and works perfectly. Just the SUB is not working. I’m struggling with this issue for months and nothing that can help to solve this annoying SONOS issue. When I check the SONOS devices at your portal all are ONLINE except the SUB.

Your confirmation number is: 782153502.

Just to make it clear, I’m just a Sonos user, like yourself.

As you have tried the suggestion of ‘bonding’ the Sub to another room and have wired the sub to the LAN and have already factory reset it aswell, then it’s perhaps best you contact/chat to Sonos Support Staff via this LINK and see what they can perhaps discover from your diagnostic report.

After hundred hours invested, they offer replace the SONOS Sub defective for a refurbished one paying ~ $400 (Originally paid ~$700) total more than one thousand. I was expecting a repair option but not. END of the history.

:(

How old is the sub? - the manufacture date is next to the MAC address/serial number? I assume it’s well outside the guarantee period, but just curious?

I see you also reported a "Sub not working issue” 3 months ago in the community here and was advised to contact Sonos Support back then - what happened in that earlier reported case?

The serial number begins 1506. I didn’t pay attention to the SUB so after I install a new TV I tried to use the SUB but never worked. I bought the SUB at BestBuy (2015) obviously is out of Warranty and I ask myself why SONOS do not provide a repair service.  I follow most of the community chats (and Youtube)  that is the reason I spent many hours. I send several diagnostics to SONOS and for now I appreciate your preoccupation but this Sonos SUB issue is part the past and I’ll look forward for something new. Thanks to your SONOS Engineering team (SME) for assigning time to check the problem.

I'm having similar issue with my sub 

I move it to plug into router and connect it, it works fine. So unplug router cable and still works fine, unplug from power move it back across the room and plug in power on wait a few mins but nothing, no bass. What's the problem here please help

It’s probably not how close it is to the router in most instances, as the sub usually connects over a 5Ghz ad-hoc connection to the ‘player’ that it is ‘bonded’ with.

What should the sub be connected to in your case? …and can you check that its player has not had its wireless radio switched off in its own room settings.

Hi Ken thanks for your reply 

Issue seems to have sorted itself out now after about 2 hours it has decided to cooperate and connected woohoo

For my particular case, at the end I bought a FO splitter, a DAC converter, and a Polk Sub ($130) and problem solved. 

Unfortunately, my Sub seems to have contracted the same illness being discussed here. A little about my system; I have the Sub paired with the Arc in the living room, a Five in the adjacent dining room, an Amp powering the backyard Sonance system, and a Beam with 2 surround Ones upstairs in the bedroom. I mostly use the system for streaming music downstairs, (which I do daily after work) so I’ll have the Arc+Sub, the Five, and sometimes the Amp all streaming simultaneously. Everything has been working beautifully for months until last night when I went to watch a movie on the living room TV where the Arc+Sub are connected. No Bass. I noticed immediately, and insisted that movie night could not continue like this. So I spent about an hour unplugging and re-plugging, factory resetting both the Arc and the Sub. A lot of the times I did this, the Arc wouldn't register the Sub and instead of Arc+Sub in the app it would say Arc+?. I ended up removing and and adding the Sub back several times. When it would finally register as being re-connected each time, there would still be no audio from the Sub. Eventually I gave up and we watched a show upstairs in the bedroom instead. So I find myself here on this forum and the more and more I read, the more discouraged I’m becoming. I’m hoping that by now there might be a known issue causing this that doesn't involve me unplugging and resetting every electronic device in the house just to find that it still doesn't work so I went ahead and submitted a support diagnostic request. Confirmation # is 1717452876. Someone save me, I need bass asap! Please, and Thanks!

I had a similar issue with my sub gen 3 that suddenly stopped functioning. No sound, no power light nada. I spent about an hour and half with Sonos support trouble shooting the issue but no luck. I was still under warranty and I was told they would replace it. I left the sub unplugged for the night. The following day I plugged it in and the sub powered up. Everything there after functions normally. There might be an internal battery that needed to complete loose it’s charge or something to clear the memory. I have no clue but I was happy I didn’t need to ship it away. 

I send Sonos sub gen 3 isn’t having 

I found the solution - works for me at least..

- unplug your SUB and leave it unplugged overnight. Plug it in and it works the next day.

prior to that I have tried factory resetting the SUB, re-adding the sub to the system, rebooting the router, but all to no avail… somehow it works when I leave it unplugged for a night. I don’t know why but it works..

After running an update, I now have no control of the sub with my Sonos app.  Not able to adjust volume.  Any suggestions?