Have you checked for any Sonos App firmware updates and tried rebooting the local router to see if that might fix your issue?

Yes and yes. Now the Amp is playing and one of the moves isn’t. Feels random. 
 

this is new. The move appears in the group list volume meter and when I press vol up/down on the move itself, the meter in the app adjusts to the presses, yet, no music is playing there (but is playing on the amp and the arc)

I’m not too sure what you mean, maybe attach a quick annotated screenshot to assist?

As an example @jvaleski are the rooms grouped like this? - see attached.

Does the desktop app see all your speakers and play to them?

edit to add the reason why I mention the desktop app is if it is working you can rule out your network and know its the buggy AF new app. It might be your network but there’s thousands of posts here about issues with the app and better to go with the low hanging first. 

@Ken_Griffiths - yes… grouped like that. I dl’d the macos desktop app and things seem a little better (I can play to all the amps/speakers), but still can’t group all of them. when I select all of them (party mode), the Moves get left out and I get a “cannot connect to device” error. if I select the Moves independetly, they work just fine.

@Bumper - bummer… didn’t know the new app was busted, though it seems like there’s some deeper issue as well.

Yes a slightly strange one - the desktop controller App hasn’t changed, so it’s likely not the new Sonos App on this occasion. First check if all your products firmware are up-to-date, via the App.

Are you using multiple WiFi access points for your Home Network, Any WiFi extenders? If so, see what happens if you power off the AP’s, so that everything has to use the main router WiFi access point only.

My other thoughts (assuming the above does not resolve the issue) is to shift the non-playing Move over to your other WiFi Band. So if it’s currently using the 5Ghz WiFi band, move it over to the routers 2.4Ghz (more penetrating/far reaching) band. That can usually be done by band steering the device manually in the router (if SSID’s are the same) - blacklisting - or if SSID’s are different, by swapping the band SSID/credentials in the Sonos App network settings - see these two support links (if required): 

https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network

https://support.sonos.com/en-us/article/remove-a-wifi-network-from-your-sonos-system

Looking like this is an issue with sonos’ networking protocol stuff and unifi networks. I just went through these instructions and things seem to be working now. Curious to see what other issues/fallout occurs though as I have 75 network devices on a multi-AP network. :/

https://github.com/IngmarStein/unifi-sonos-doc

Yes, there are also these instructions from the manufacturer Unifi…

https://help.ui.com/hc/en-us/articles/18930473041047-Best-Practices-for-Sonos-Devices