I have same problem - reported it to Bose 2 days ago. You should try calling Bose so they put more attention to it.
See my post at: https://community.bose.com/t5/SoundTouch-Speakers/Problems-with-Amazon-Music-on-soundtouch/m-p/11949...
I'm pretty sure its from their app update in late March.
Hi Jens72 and mbmusic,
Thanks for the posts, and sorry to hear about the issues you're having.
The update we released at the end of March only contained a fix for Norwegian language users:
A minor interface update (18.1.6) was released to correct an issue where it was not possible to create a new SoundTouch account in the Norwegian language.
Can you try removing and re-adding the accounts to your SoundTouch app? As well, do you get any error messages when you try to play music?
Let us know so we can get this resolved.
Best,
Brandon - Community Support