I encountered the same issue.
Everything works great at home, but when I added a Dot at school, it gave me that error.
Even when I tried to play things directly from my list on my phone (via the app), nothing.
At my school, the have a filter that blocks most music streaming services. This part of Amazon's service is blocked, but not other things like general questions, Lists, etc.
If you are experiencing this error at home, call your ISP (internet service provider) and ask if it is being blocked. If you live in apartments or condos, they can control bandwidth in this manner, but not if you live in your own home.
If you are getting this error at work, then I would say they are definitely filtering to improve bandwidth for 'actual' work.
Although there is much research that people work more efficiently while listening to music.
I hope this helps.
((LLT))