I've been having a consistent problem with the spotify app on iOS. 

Starting from a fresh install, I login to my account, and am able to see ALL my Sonos speakers at home (3 speakers) and the office (3 speakers) from the devices menu. However, if I toggle playback to offline mode, they disappear, which is expected. IF I then switch back to online mode, the devices still do not appear. I've tried

1) restarting the app

2) rebooting the device

3) rebooting the sonos speakers / network router

4) re-authorizing spotify on the speakers

None of this works. If I use another device (iPad, web player on laptop) the devices also DO NOT appear. 

The only methods that restore the devices are

1) Logging into a different account on the device

2) Uninstalling the app on the device and then re-installing

Neither of these solutions are acceptable and this entire process is pretty repeatable. It appears to be an account level bug since it persists across devices once one is put into offline playback. It is almost like the account doesn't recognize that it isn't running in offline mode anymore once it is toggled back.

Another oddity is that once I put a device into offline mode, and then back to online, the device seems to always show up as an offline device in the account. If I toggle into offline a second time, the SAME device shows up as a second (and then third, fourth, fifth) offline device