Just a heads up that I installed the new Sonos 7.0 public beta over the weekend with direct control directly from Spotify Connect. It looks like the plug in sees all the players but is not able to get any current status from the players.
I'm currently downgrading back to 6.5.x right now so that my house isn't broken... but I thought I'd give you a heads up that it seems like a few breaking changes might be on their way.
That said... could just be a bad beta build and your plug in will be fine with the final release, whenever that comes. Who know