There is no fix. The Move is designed to be set up on one WiFi network, which is typically your home network. Then when you take it portable outside of the range of your home network, you use it in Bluetooth mode.

I thought Sonos speakers could remember more networks since the Move was introduced. This is acknowledged here: 

Or am I misunderstanding the problem?

The Sonos Move will support upto 16 different WiFi networks - to add a new network to it see this link:
https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network

The danger here though is that the device will ‘highly likely’ jump between the two (nearby) wireless network subnets, particularly as it is a portable product …and I foresee it causing problems - I would personally only ever broadcast one WiFi network, or the other, at any one time if you do decide to add both networks to any of your Sonos products.

I use multiple networks myself (see attached) but in my case they are not in range of each other, or at least are never broadcasting in the same location, at the same time.

Ken, 

I, of course, had seen these instructions, and followed them with no avail prior to posting my issue. The Move was unable to connect to the second WiFi network (miles from the home network), which prompted my support call to Sonos. As I explained, Sonos support stated that I would need to factory reset the Move each time I wanted to move it between the two networks, which is an insufficient solution. 
 

My original issue stands unaddressed. 

Does the other network conform to Sonos requirements?

https://support.sonos.com/en-us/article/recommended-settings-for-using-sonos-on-wireless-networks

https://support.sonos.com/en-au/article/sonos-system-requirements#

Oh, brother.  I can tell that we’re getting into the weeds now.

Netgear Orbi RBR750 mesh network, so, yes, complies with Sonos’ requirements as I read them. It’s not a complicated setup. As I noted in my original post- none of my or any of my friends’ or family’s other devices have any issues connecting to this network - even basic IoT devices  

I just want Sonos to address the shortcoming with a bug fix. I refuse to resort to factory resets to accommodate a Sonos bug. I’ll buy another product first. 

Works here for me … I have added several WiFi networks to my setup, as per the earlier attached image. I can be hundreds of miles away from Home and add any nearby ‘compliant’ WiFi network to my Move/Roam etc. If you’re having difficulty following the Sonos connection method you could perhaps try this alternative approach instead …

Try these three steps…

1. Whilst still at your Home ‘A’, simply add a mobile Hotspot (WiFi = iPhone-Hotspot) to the Sonos setup via ‘Update Networks’ in the Sonos App Network settings.
2. Then transport Sonos Move/Roam etc; to Home/location ‘B’. When there, first connect the Sonos controller device (an iPad for example) and the Move/Roam speakers to your mobile Hotspot (WiFi = iPhone-Hotspot)
3. Next add the (now in range) Home ‘B’ WiFi to the setup via ‘Update Networks’ in the Sonos Controller App and all will then work on the new WiFi. (Post transfer, switch off mobile hotspot and connect mobile controller (iPad in this case) to the Home ‘B’ WiFi).

CMacG,

I have no trouble moving between networks, there is no need to Factory Reset.

There are two WiFi’s in my house. Today, as a quick test for this post, I added the second WiFi to one MOVE using an iPad. I was asked to enable a direct WiFi connection to that speaker. I selected my second WiFi and gave the password. At this point the system wanted to drag me through adding the second WiFi to each of my other speakers, but I declined since this was only a test. This flustered the controller a bit. I allowed a little time for the system to work through some details, then force closed and restarted the controller. At this point all of the players had been moved to the second WiFi. There was no Factory Reset.

The system is docile about this. Until a couple weeks ago I had been using the dual WiFi, but deleted one of them from the SONOS system as a test. Today, I simply added the deleted WiFi back into the SONOS system. Even while I had deleted one WiFi from the SONOS system, I could still use a controller on either WiFi.

Your second house will be similar. Likely there will be a complaint about missing players at the second house because you are only carrying one player with you. Just select the player that you brought with you and add the new WiFi. There will probably be a complaint about “missing” units that you can ignore. Years ago I took a MOVE to another location and had no problem using that WiFi. In fact when I brought that unit back home, the new WiFi was added to all of the players and I could simply walk another player to that location. None of my current players have ever been to that other location, but all are aware of the location.

—

A note: Setting up two WiFi’s in the same house is not quite straight forward and is rarely recommended or necessary, but it’s not hard. As stated I can use controllers on either WiFi. I know that Ken (and others) have similar setups and none of us have issues with it. Setup incorrectly, this dual WiFi can introduce major issues. Community regulars have bailed out legions of users who accidentally fell into this situation.

Is the Move the only speaker at each location (in which case it should be able to connect to different networks) or do you want it to connect to other speakers at each location - in which case Sonos don't support you ‘Move’ing (or ‘Roam’ing) between systems unfortunately, even temporarily (although I believe this functionality has been requested).

True, a speaker cannot freely move between systems, but a “system” can be split between locations. There are some nags while doing this, but they are not showstoppers.