Just a note for others, my SiriusXM account just stopped playing this week on SONOS, and per the advice here on the community and then from SONOS Support (Case #02556297), I tried removing and re-adding my account credentials as a music service. Then tried changing my password and waiting 24hrs as instructed by support. None of this worked; I still could not play SiriusXM over SONOS - just kept getting an “Account not Found” error. It would play fine on any other device or app, just not SONOS.
Today I tried also changing my SiriusXM Username along with the password, and it worked immediately, I could re-add the account on SONOS. What seems to be the key here is changing the Username, not just the password, I assume that causes a refresh with the account credentials database.
Very frustrating that SONOS support could not advise me of this apparently critical step when contacted.
I still have no idea why my setup stopped playing SiriusXM after years of continuous use...but this seems to be the steps to getting it back online with SONOS.