This is a strange one and I haven't found anything about it online.
I have several speakers/zones in my house. They work fine as groups or independently with every Sonos service except Amazon Music.
For some reason, Amazon Music only plays out of 2 of my speakers, which are part of a zone that has 3. And all speakers indicate that they are playing but only a specific 2 emit any sound.
The 2 speakers they play from are a Playbar and some in ceiling speakers via connect amp. It's my only Playbar but I do have other speakers using connect amps. So it doesn't seem to be a device specific issue.
Bizarre stuff. Anyone heard of anything like this?