I have my living room set up with a Playbar, Sub, left and right surrounds Play 3. Often when I play a song it sounds like only the playbar has output and then maybe 30 sec later the sub comes in. I've dicconnected and reconnected it a few times. No change.
I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
What happens if you unplug your Play 3s from power and then power-cycle the Playbar and Sub?
Folks have been mentioning Play 3 glitches recently and that would remove the possibility of that being your issue with the Sub.
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