The ‘discovery’ of the Sonos products by the Sonos controller App can sometimes be a slightly complex area to explore, but briefly… 

SSDP (the UPnP simple service discovery protocol) is used to initially discover the Sonos players and is done via multicasting via UDP to 239.255.255.250:1900 and, for good measure, broadcasting to 255.255.255.255:1900. 

Both the Sonos players and controllers must share the same network subnet. However if the Sonos devices are connecting to multiple access points, the recommendations (from myself) are that they be set to the same WiFi channel and channel-width. This is for optimum performance particularly in groups and for some reason with some (not all) mesh-based WiFi systems, it appears some will work okay with Sonos, but others may not, particularly if the satellites/AP’s are perhaps auto-selecting their own WiFi channels. I’ve seen some people report issues with Google ‘nest’ mesh WiFi, for example, although others will occasionally say it works for their ‘small’ Sonos setup.

What is certainly not supported though by Sonos, are wireless range extenders, as some can mangle device MAC addresses and EoP (powerline) adapters.. so if you are using those type of wireless access points, to extend the wireless network coverage, then that may cause such intermittent device discovery issues by the Sonos Controller App.

Reserving the IP addresses in the routers DHCP reservation table can often help with device discovery, so consider making your Sonos IP addresses static. The router user-manual will normally assist you to do that in most cases.

Just to add aswell, it can sometimes be Apps/software running on the mobile ‘controller’ device that interfere with ‘device discovery’ Examples to perhaps consider are…

• VPN Client 
• Firewall software
• Antivirus software
• WiFi Calling/Dial assist
• Private network address (MAC address spoofing)
• Mobile data enabled for the Sonos App  

So consider disabling these features, even temporarily, just to see if that may fix your device ‘discovery’ issue.

Ken

thanks. I will try hard IP addresses 

still baffled the Only issue out of 9 Sonos speakers that I have repeated issues with

Just to add one thing to @Ken_Griffiths list of possible reasons:

Sometimes I saw people running in such an issue because an IP was listed twice on the routers IP list. Deleting the one and giving a new static one to the device or via DHCP sometimes solved the problem. 
So imo a check for double listed IPs also would be worth a try. 

@cooperd5908,
If you do still encounter a problem and you think there maybe a fault with the product, then (when the Roam is showing in your App) you can always submit a Sonos system diagnostic report from within the Sonos App, note it’s reference and then contact/chat with Sonos Support Staff via this LINK and see what the Staff can perhaps suggest to resolve the matter.

I caught my router pulling this stunt. An unreserved SONOS ROAM pair was given the same IP addresses reserved for two unrelated clients. The reservations were made a year or so before the ROAM’s were installed.

Update.  

I gave every Sonos device in the house a static IP. Repowered speakers and router.  All devices confirmed with new static IP.  Worked for a bit so, I put the roam back on the charger while playing.  Got up this morning, Roam still on charger still has white light.  Open App - No Roam.

Take Roam off of charger - No Roam, Press Power button light goes dark, press again, get white light and Roam shows in app as asleep. Back to same old problem, it would still play music from another group of speakers even though app says its asleep.   So then do a 5 sec press, Roam comes back on and App now sees it.  WHAT A PAIN.  My MOVE has never done anything like this. It apps that in order for the App to see it (see everything else) the Roam needs to be totally reset every time you want to use it.   This problem is about a month old. It never did this before and the move doesnt so still thinking it is an app issue.

Thanks

Doug

PS: also confirmed no duplicate IP’s, and Router is Netgear MR63.  

In general routers will not report duplicates, although some will. My router tends to attract ‘fires’ when you search for it on the Internet. I have made it a practice to reboot the router once a month.

It may be productive to Factory Rest the ROAM. As you restart it, take care to add it to an existing system, don’t accidentally setup a new system.

You’ve certainly reduced the variables, which helps. If @buzz ‘s suggestion doesn’t work, you’re in a better position to submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

I have 28 active devices on my router.  I bought the roam ( two actually, as I thought the first was defective) To use as a portable Bluetooth speaker.  Setup requiring configuring static IPs!   These devices are horrible and near impossible to configure.  I spent hours with Sonos support and they couldn’t get either one of the Roam devices to configure.  No wonder they are being discounted and hopefully discontinued.

I have had 4 Roams.  3 have died ( just don't turn on).  SONOS replaced one I had under extended warranty.   I would not buy another and am disappointed Sonos did not consider a recall as they definitely have a lemon in this product. 

Yep - mine just died.  Doesn’t power on, doesn’t reset, doesn’t show up in the app.  Nothing, nada, zip, zilch - paperweight now.  WTF?

Mine died also, seems as if the power button does nothing. Get red flashing charge light when plugged in to usb c.

The same - red light is on when plugged into USB or Power - unplug, paperweight.  Absolutely no change in device since using it a month ago and now it’s useless.  No combinations of button holding, pushing and releasing etc does anything.  Ugh!

I tried chat support yesterday, after 20 something people before me, guy said to do all the resets, etc that I had already tried. Nothing worked. He told me to charge overnight, which I did. Of course I did this before but I did it anyway. Tried call today but I was not going to wait the stated 60 minutes just to hear the same useless instructions. Really disappointed as my 5 other older Sonos speakers have never had any problems. They should have recalled all of the Roams as they seem to fail after the warranty has expired.