Now confirmed, that was the problem (forehead slap). Speakers are now working. I'll report back after I get a chance to sit down and do some serious listening. Thanks to all for the quick responses.

Main System: MD600 & Sonos Connect -> 818v2 -> DSP5200SE+DSW SUB
Alternate Main System: Sonos Connect AMP -> Dynaudio Contour 1.3 SE speakers + Sonos SUB
Kitchen: Sonos Play:1
Bathroom: Sonos Play:1
Bedroom: Sonos Play:3