Im trying to set up Yamaha MusicCast Devices to play Spotify through Amazon Echo Dots. I have 2 MusicCast 20 speakers and a RX-V585 receiver. I can play Spotify on all 3 devices through the MusicCast app and by using the devices selection in the iOS app. 

However, I cannot seem to get them to play through my Amazon Echo Dots (I have both a v1 and a v3). All my Yamaha devices will play Amazon music but Spotify is the only service I typically use. 

I have tried uninstalling and reinstalling the Spotify skill but that did not seem to do the trick. All (both Amazon and Yamaha) have up to date firmware. 

any help would be greatly appreciated! Thanks!