Your diagnostic number is probably removed from this forum because this is a public forum, not a method to communicate with support, they don’t monitor here. Your best bet, with a diagnostic, is to call Sonos Support directly to discuss it. The Sonos forum moderators are few, and while they sometimes have the time to pick up a diagnostic and respond, I suspect they have their hands full monitoring posts right now for violations of Sonos’ posting policies. 

Did you follow the information in the new router - installation instructions FAQ? One of the most important aspects, when replacing a router, is the reboot of all devices connected to it. What you’re crudely describing certainly has appearances of a duplicate IP address issue, I’d likely unplug all Sonos devices from power, then reboot the router, and then wait a couple of minutes before plugging each Sonos back in. This would force reloads of firmware on both the new router and the Sonos devices, and cause the Sonos devices to ask for new IP addresses from the refreshed router. 

Tried your suggestion above - doesn’t work. Same issues persist. I’m literally at the point where I’m thinking of getting rid of Sonos. All this money for a system that can’t function properly….