Bluesound

I am dealing with the same issue 

Update:  I hooked up the WiiM Ultra, streaming from Amazon.   It appears to be working "OK" although the lag time when you select a different track is much longer than the way Bluesound used to work.  I noticed a couple of times the song had to be pressed a couple of times before it would play.  The album cover shows up on the device before the song plays.  I was jumping around quite a bit changing songs to try "break" it  to see if it greys out etc but that has not happened (yet).    This is a very prelim assessment since the WiiM just arrived but it is functional with Amazon.  I have only used headphones to test it so no comment on sound quality although the sound through inexpensive headphones sounds quite decent.  So .... either the Bluesound implementation of Amazon is broken or BlueOS v 4 and its app are junk.  The WiiM unit appearance is nice, but the box feels plasticy.  For  $327 don't expect much more.   

Further update WiiM Ultra.  I have continued to try break it.  Frustratingly, I searched for all Paul McCartney albums and it returned just 4.  Looking at Amazon Music on my PC, there are dozens.   I tried Paul McCartney and Wings and it returned No Results.  It looks like the WiiM implementation of Amazon is also lousy.  It would be nice if Amazon would build an Amazon Connect to get around these streamer issues.  So I am wondering if it is simply too difficult to use Amazon.  May be worth looking at Tidal Connect.  

I switched from Amazon to Quboz after the last software update crippled AMHD. Things that I thought were BluOs related are actually shortcomings of the streaming service itself. Sometimes I search for something under the artist name and nothing comes up, but if I search for the specific title it finds it, but it's still not showing under the artist releases.

I suspect the issue is with Amazon, not BluOs. Not enough servers, app updates not yet shared with external services,etc. If you like your Node, I would be a little patient. 

A simple workaround is to add what you want in the Amazon app as a favorite, then open it in BluOs from your library. Then you can save it as a BluOs playlist. 

This error popped up for me a number of times when I was trying to use Amazon Music - BluOS blames it on a faulty API on the Amazon side, and they don't have a fix for it. I had enough of the wonky Amazon/BluOS interface and switched to Tidal, with no similar issues since that switch.