Are you logging in under the same account? Are you connected to your network? If all the above is true try unplugging all devices and rebooting your router and then refreshing the Sonos app. Afterwards plug each device into power one at a time to see if they reappear.

EDIT: Do not factory reset your products as doing so requires you setup your system from ground zero.

I’d be tempted, at least in the beginning, to ensure one device is wired directly to the router with an Ethernet cable, which could be either a temporary, or permanent thing.