It does work fine for me, but only if I use an AirPort Extreme, if I switch to my isp supplied router it just doesn’t work. I assume it’s something to do with loop back.
The difference between the airport and the isp router is obvious as when you use the sonos app it can’t play any plex tracks. However everything else works like remote access etc with either router. Didn’t matter if it was manual port forward or upnp sonos never worked on the isp router.
Whether or not that’s the problem you have I don’t know.