Yesterday we released the 5.5 version of our Sonos Controller. While on Android you will be offered to reauthorize your Spotify account directly via a link, on iOS you will only receive a notification without direct link to the reauthorization process.
To complete the process on iOS, please follow those steps:
1 Go to Settings on the Sonos Controller
2 Select Services or My Services (depending on the Controller being used)
3 Select Spotify
4 Select Reauthorize
5 Follow the on-screen instructions to reauthorize the Spotify account.