What kind of extension devices?
Any chance you might explain how you resolved your issue, on the offhand chance there is someone else who comes along to read this thread, who might be experiencing the same issue?
Two networks were identified to the sonos app. Speakers furthest from the modem connected via a stringer connection on the extension. The speakers that responded to the app where the ones on the wifi vis the modem.
in settings i went to networks and deleted the extension wifi leaving only the modem wifi. All speakers then picked up on the main network. All responded to the app.
sonos dont always work on ext network, and if 2 network connections are identified to the sonos app and speakers arent on the same network id must be the issue.