We'd suggest you restart the devices and then to log out and log back in again. If that doesn't help, you can give these steps a go and run a clean reinstall. This one is more thorough than the usual one.
If the issue persists, it's a good idea to restart the router.
Let us know how it goes. If you have questions, you know where to find us.
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"Difficult roads often lead to beautiful destinations." ―Zig Ziglar
I have been having this issue for almost 12 months off and on. Will work fine for months and then just start randomly happening. Sometimes just turning the speaker off and on will solve it, I have 6 assorted Bose Soundtouch speakers and it happens to different speakers. I have done factory resets to fix it (sometimes works, sometimes doesn't), but issue will pop again. Interesting that it is with spotify only. Have used the Bose and Spotify connect apps on android, PC and iPad and all have the same issue. Is there any way to stop this other than switching streaming service?