The 8.2 BAS speaker is shown in the documentation as a ‘passive’ Bass speaker. Looking at the Sonos Amp literature, it only supports third-party ‘active’ subwoofers, so that will be the reason it’s not working for you.

Thanks Ken, but I only use the 2 main speaker connections (like I did on the old Connect:Amp) to use the sub’s built-in crossover (getting the full range signal from Sonos).

Ah I see - I assume you have perhaps tried adjusting it’s crossover and phase switches to see if that may improve things?

If no joy with adjusting it’s crossover, then you may need to somehow add a separate Amp to drive the Sub as briefly outlined in this other thread I found…

I connected with https://www.ceiling-speakers.co.uk/ , where I bought the speakers.

Jason quickly told me that others have had a similar problem, which can be caused by not phasing the 2 outputs correct. When that happens the Subwoofer cancel itself. Switching the lines on one of the speaker outputs solved the problem.

Thanks for the feedback here @johnshansen. That’s well worth remembering and hopefully will be helpful to others too.