Have you considered the possibility of a router software update? Or TV firmware? Or a neighbour’s wifi clashing with yours? 
 

If you’ve reset the speakers there’s no point submitting a diagnostics for Sonos to check out as the reset deletes any potentially useful data. Maybe power down everything and then a phased restart. Start the router and wait for everything to reboot - including wifi. Then start a Playbar, and then the surrounds. Also restart your TVs. 

If the above doesn’t work try running a temporary Ethernet to one of them at a time and see if that helps.

Do you have them on good quality surge suppressors? Both going at once, if none of the above work, could be power spike induced failure.

Yeah, tried everything. As I said, nothing in my house / router / system / neighbours wifi / “Pixxies sprinkling the playbars with magic dust in the night” has changed. Older speakers, further from router working fine.

One of playbars (slightly newer) magically fixed itself….but after an hour online to sonos help….seems that the other one is bricked.

They made a point about how it was 8 years out of warranty and how they would helpfully give me 30% discount on a replacement.

Hard not to suspect they sent a “brick code” to make my old playbar unusable….

I can get a replacement cheaper online…but will now replace with a stand alone sound bar / surround system for ½ price…..as although I’ve been a loyal Sonos customer for over 10 years….there’s no way I’m throwing $1000s more at sound bars which can magically become bricked with no way to repair out of warranty….

Both of the two PLAYBARs I purchased within the year of original release are still working fine, so it’s hard to believe a concept in which Sonos sends out a “brick code” to any device. Without needing to put on my tinfoil hat, it’s a bunch easier to believe @Stanley_4 thought process than yours.