Are you trying to stream music on the Sonos speakers and Echo devices together? If so, this is not possible.
I have the same issue and am not trying to play on Sonos & Echo at the same time. This is a recent change/problem as my system setup hasn’t been modified in years.
I am/was using the Echo dot device to initiate the music to a “dumb” group i.e. 2 x Play 1 & a SUB (no voice control) and it would happily play the music to the group and the Echo dot just acted as an initiator. Now it plays on the Echo dot only! Previously I could put this group as my prefered speaker now I can’t even tell Echo Dot to play the music on SONOS.
The Alexa app advises that my SONOS speakers are not capable of playing all Audio types!
My dialogue with SONOS suggested they had no idea what I was talking about and eventually ended with a Group cannot consist of more than one speaker if it is going to work with the Echo Dot!
Don’t know if it is a bug or if it is deliberate and if the latter shouldn’t we have had an option to not go to the latest version of the S2 software or latest version of Alexa or at least have been told about the change?