Have you added Spotify as a music service in the Sonos app?

Yes, and I have removed it and re added and re authorized it several time. 
 

thabks 

Do you have the same problem if you play music to your Sonos speakers through the Spotify app?

Yes same problem, if I airplay to the speaker it works, but not through the network. 

How long have you had this problem? It could just be a temporary issue with Spotify.

Are you able to connect one of your speakers (not the Sub or any speakers used as surrounds) to your router or network with an ethernet cable?

I have been having the problem for a few months, and can’t see any posts saying there is a Spotify issue. 
 

I can get on plugged into my network switch with an Ethernet cable. Let me try this out and see what happens. 

same issue since november

I have the exact same issue as @Dylanmc00

I’ve got two Sonos speakers, Beam and Play:5. Works with no issues over Airplay. They both show up as devices inside Spotify Connect, however when selecting to play Sonos Connect through the speakers it fails. Doing this through the iPhone gives a “Connection to Spotify was lost” after a few seconds of selecting a song. My Play:5 is hard wired and Beam is on Wifi. Both devices used to work fine, this issue has been present for about 3 months. I’ve updated everything, re-authorized Spotify several times. Wish there was some better diagnostics tools. It’s as if the local connection via device and speaker is fine, but the speakers can’t connect out to Spotify. Grateful for any tips.