sonos amp issues

Is this a new setup, or have you had them all working before but now they’re not? 

Are both pairs of speakers 8ohm? 

These are passive speakers, so there’s no way to know they are connected OK from the app.

Are the physical connections seated right? 

A SONOS AMP is a normally configured as a stereo device with left and right outputs. If four speakers are connected, there will be two sets of wires connected to each AMP output. These connections could be make in the back of AMP or somewhere in the external wiring.

Are there any Volume controls in the external wiring? Some installations have in-wall Volume controls for each room.

As a test, try to adjust the left/right balance. If one or the other side is silent, there is a wiring fault. The fault could be immediately behind AMP, in the external wiring, or wiring to (if you are using one) an external Line-In device wired to AMP.

If you can see the amp in the Sonos app then WiFi has nothing to do with your issue. The problem lies with the passive speakers and/or the connections. As a test try switching the active speaker terminals with those of the inactive ones. If the previously active speakers play as expected then there is a problem with the inactive speaker connections or the speakers themselves.