I had the same problem! The SoundTouch appeared in the "Connect to a device" list successfully for around 3 or 4 years, without fail. In fact the SoundTouch was the device that was always available when other devices like my Rocki play (so unreliable) or OnePlus6 (excessive power saver) were flakey as.
Then one day, my faithful SoundTouch speakers just stopped appearing. Disaster! With no notice, no error. I only knew it had dropped because all of a sudden Spotify was showing no devices on the list and instead offering me patronising 1-2-3 guides on how to connect a speaker! SERIOUSLY! I had to listen to music on my laptop speakers for almost half an hour!!!!!
I tried everything. Installing latest firmware. Reconnecting the Spotify account. Restarting my mac book and phone. Even rebooted my router. Nothing fixed it. Then, in a fit of frustration, I did a cold restart on speaker. Ripped the cord out the mains. Let it reboot. And low and behold, the old faithful speakers re-appeared.
And again, after 45 minutes of tinny music and two Ecosia searches, all was again well in the world.
By ripping the cord, he means simply pulling the electrical cable out of the back of the soundtouch, waiting a few seconds until all lights are out and plugging it back in. Alternatively you can pull the plug out of the wall socket, but not all of us had access to it. Main thing is, leave it unplugged until all the lights go out.
Spotify will not work through my Bose system anymore. Pandora works fine. I’m suspecting has nothing to do with those but with Spotify. Please fix the problem since I am paying a monthly premium due for Spotify!