You’ve not provided any information to us about your network, but I’m going to hazard a guess that you’ve got some sort of mesh going, and your desktop is connected to one subnet, while your phone controller is connected to a separate subnet. 

Have you tried to call Sonos Support directly to discuss this issue?

Same. 

Desktop app recognizes my kitchen Connect but not my two bedroom speakers. Same wifi throughout. I can play my library (on same desktop) in kitchen but not through speakers - can’t find the files. 

Spent about 20 hours this month reinstalling system to get iPhone app to work so very hesitant to do more rebooting/reinstalling. 

What did Sonos support say, when you contacted them?

That’s next. Been working so tough to be on hold. 

Rebooting my mac and wifi a few times last night got the desktop and iPhone app to recognize rooms and library. Full functionality. This morning though I’ve got one of three devices recognized on my phone. Unplugging and resetting the speakers a few times usually resolves that - although the desktop app recognizes them but not iPhone. 

That suggests a slightly different network connection to the router between the two devices, as a guess. Possibly a mesh network issue? Sonos really needs to be on the same subnet, but I’ll be curious as to what customer support has to say.