We are using the music version that comes included with Amazon Prime. Which works great with our standard, (tall), Echo. My wife purchased Amazon Prime under her account. We added me through Amazon's, "family member," option so I can order with my account separately as we've done before, but everything is jointly shared under Prime. Even our Kindle books are now shared. She bought my Echo and I downloaded the Alexa app on my iPhome, installed everything, and the Echo works fine with Prime Music. I gave her a Dot, she downloaded the Alexa app on her iPhone, installed everything, and her Echo dot works just fine except it does not recognize our Prime Member Music as mine does. When I look into my Alexa settings under music, I see Prime Music. When I look the same place on her iPhone under Alexa settings it only shows her music library, (which is accessed fine), but NO Prime Member music.
So.....I'm trying to get her Dot to see what mine does.
Hope that helps, Dennis