It’s true that Sonos do not officially support WiFi extenders, as stated in their system requirements, but no doubt some WiFi devices out there may work. What you haven’t mentioned in your post though, is if you have added the new WiFi network SSID/credentials, (extended or otherwise), to your Sonos device. I would recommend you wire the Connect:Amp temporarily to your new router and add the new wireless network to it, via the Sonos App, using the instructions in this Sonos Support link…
https://support.sonos.com/en-us/article/connect-sonos-to-a-new-router-or-wi-fi-network
Once that’s done, ensure your extender is broadcasting the ‘exact’ same SSID and has the same password. I also recommend the router and extender use the same ‘fixed’ non-overlapping WiFi channels (1, 6 or 11 for the 2.4Ghz band) and the same 20Mhz channel-width for that band.
Once the new network has been successfully added and any changes made to channels etc; you can then uncable the Connect:Amp and allow it to run on either your ‘router’ or ‘extender’ WiFi signal.
Hope that’s easy for you to follow and that it gets the Connect:Amp back up and running for you.
