Came to this thread because this is suddenly happening to me as well, music stopped playing around 3 hours ago and now every time I try to play it just says "Spotify failed to connect". Android phone (Google pixel 3), this has been working for me for approximately six years with no problems.
That did not work for me either. I have 2 Sonos 1 speakers that were working perfectly and all of a sudden yesterday jus stopped. I've tried all possible fixes here but nothing is working. It works through the Sonos app but not through Spotify. What is the deal?? Anyone?
Reupping that I'm having the exact same issue, and on this same timeframe. Google Pixel 3a; Windows 10; Sonos App -- nothing connects to Spotify. Like one of the previous posters, I got a connection for like 15 minutes that then--just as suddenly--went away. I've rebooted the rerouter; removed and reinstalled the Spotify service from the app; reauthorized the service through the app. When I ask for Spotify I still get, "[long pause]," phrase of success ("alright, here's the Spotify playlist called XYZ,"), followed immediately by "Sorry, I couldn't reach Sonos."
I've had the speakers for about two months and this has worked great that whole time until now.