Best answer by Jeff S
It sounds like your extended network isn't forwarding all of the traffic. If your extender is set up to use its own DHCP server, it will separate your network into 2 subnets. Sonos components can't communicate from one subnet to another. You may be able to set up the extender into bridge mode, which would make its wireless name, channel and password match your main network. Also, with DHCP disabled it should allow your controller to communicate with your speakers.