I get this issue on and off every couple of weeks when my iPhone won't connect to my sonos system
My iPad, iMac and fire tablet all work fine
i have removed the sonos app on the iPhone and re installed and still not working. re booted iphone, disconnected the wifi etc after a few days it normally reconnects
Best answer by Keith N
Either way, I believe having a technician get a closer look at your specific network in real-time would be the best (and fastest) way to get this sorted.