Just to share the results of a recent experiment:
A family member got a new Echo Flex (all-in-one Echo plug-in unit with tiny speaker), and wanted to test it with the Sonos speakers. They added the Sonos skill to their Alexa account and registered to the Sonos account with the speakers, the same one used with our other Echo units on a different Alexa account. Surprisingly that worked fine. The new Echo Flex was able to play music on the Sonos speakers, and the ability of the other Echo units to do the same was not impaired.
For 24 hours, that is.
The next day, the Sonos speakers had gone offline in the original Alexa account and could not be used. Unlinking the skill and re-linking did not work - Alexa was unable to discover the speakers. Unlinking them from the new Echo Flex account and trying again to re-add them to the original account also did not work.
Eventually we discovered that the “offline” speakers must be completely deleted from Alexa, then the Sonos skill removed, then the skill relinked. At that point they are rediscovered as new speakers. Apparently there was a lingering presence of the original “offline” speakers in Alexa that prevented them from being added as new speakers while also not reconnecting successfully to the original versions.
(These Sonos speakers are using Google Assistant as the voice assistant, so this is unrelated to Alexa as a voice assistant - Alexa strictly using the Sonsos speakers for media play.)
- Sonos speakers cannot belong to two Amazon Alexa accounts at the same time. It may appear to work initially, but will fail within 24 hours, with the speakers going Offline in the original account and the connection permanently lost and unrecoverable (must be re-added as new speakers).
- To move Sonos speakers between Amazon accounts, you must de-register and completely delete the speakers in the current account under Devices, THEN remove the Sonos skill from Alexa. Then add the skill and the speakers to the new Alexa account. You do not have to do anything in your Sonos account. Reverse to move the speakers back to the original account as new speakers.