To be able to advise you more precisely, we would still need that additional info that @Alex mentioned above. Also could you check if all devices in the household are using the same internet network? Any screenshots or screen recordings would be very helpful as well.
We'd suggest that you restart your amplifier and make sure it's connected to the same network as the your wife and son's devices, so that the Connect feature will be able to detect it.
On this page here, we have detailed info on pretty much all available options to listen and broadcast music via the Spotify app, could you check if your family members are able to connect to the amp via Bluetooth for example?
Hope this helps. Let us know how you get on.
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