Nothing important is stored in the controllers. A copy of important details, such as playlists, is stored in each player.

EDIT: Rather than starting with a Factory Reset, pop the battery out for a few seconds. In general with SONOS products Factory Reset, while it might accidentally work through an immediate issue, is usually not a permanent fix.

CR200’s are past EOL (End of Life). A typical issue is that screen touch sensitivity degrades in the lower right screen corner and slowly spreads diagonally, in an ever expanding area, to the upper left.

Note that the CR200 only works with S1 firmware. I’d be very reluctant to update player firmware if I was using a CR200. Maybe another user has recent experience with this. 

A copy of important details, such as playlists, is stored in each player.   I don’t have Sonos speakers, etc.  Sonos feeds my non-Sonos stereo system.  What would “stored in each player” mean in that context?  Thanks for your informative reply.

What model SONOS components are in your system?

The Sonos CONNECT and Port are considered players, but we tend to use the term ‘speakers’, since the large majority of Sonos devices in use are actual speakers. 

As ​@buzz suggests, essentially no data is stored on any ‘remote control’, such as the CRxxx, or the mobile and desktop (and web) controllers. 

Do not Factory Reset anything without further consult.

Buzz -- Thanks! --to answer your question, My only Sonos products are two ZP80s.  One was connected to my router in a different room from my stereo system, but the engineer who (successfully) fixed my problem told ne to disconnect it from router but leave it turned on.  The other ZP80 is connected to my stereo system, so the only link between Sonos and cyberspace would appear to be via wifi.

A CR200 will not work in this configuration because it is not a WiFi capable device. The CR200 must use SonosNet which is disabled because neither of your ZP80’s is wired to the network. The original ZP80 design required SonosNet, but over the years the firmware was updated and ZP80’s can now use WiFi. When the ZP80 was updated to incorporate WiFi, CR200 was already approaching EOL and was not updated.

I don’t know why you contacted support. I suspect that a wired network connection of a ZP80 has failed and you are lucky enough that WIFi still works. As a test, power down one ZP80, wire the other ZP80 to the network and try using the CR200. Next, repeat with the other ZP80. Only one ZP80 should be powered and wired to the network. During the test, verify that the ZP80 network port status lights are active. Be sure to try both network ports on each ZP80.

Another possibility is that there has been a physical change in your home and SonosNet can no longer cover the area. WiFi has greatly improved over the years and may now provide adequate coverage for the ZP80’s, but CR200 is stranded (if it’s still working) because it cannot use WiFi.

Is one of the ZP80’s not connected to any audio devices?

Yes -- the one that was (until recently, as described above) wired to the router is not (and never was) connected to any audio device.