I have a similar issue, but not quite the same. Instead of playing on my dot, it just gives me an error message. This seems to happen whenever I ask it to play Pandora to a group. I have Pandora set as my default station server and a station on Pandora called Adele Radio.

It works playing Pandora to an individual speaker:

Alexa play Adele Radio in the Kitchen (plays station, confirms source as Pandora station)

Alexa play Adele Radio from Pandora in the Kitchen (plays station, confirms source as Pandora station)

Alexa play Adele from Pandora in the Kitchen (plays artist tracks, assume this is from Pandora)

It works playing non-Pandora to an individual speaker:

Alexa play Adele in the Kitchen (plays artist tracks, but believe this is Amazon Music, my music default)

It works playing non-Pandora music to a group:

Alexa play Adele Inside (plays artist tracks on my Inside group, but believe this is Amazon Music)

But it fails playing, playing music from Pandora to a group. All of these give me an error that she can't find the group Inside.

Alexa play Adele from Pandora Inside

Alexa play Adele Radio Inside (default for stations is Pandora)

Alexa play Adele Radio from Pandora Inside

---

Groups are not supported yet, either via Sonos grouping or groups in the Alexa app. To play to grouped Sonos speakers, group via the Sonos app, then ask Alexa to play to any individual room in the group and it will play to the entire group.

---