Might be worth a reboot of your router, followed by your speakers. Since any supposed fix would have been done by SiriusXM, it may be worth checking directly with them. 

Rebooted router, unplugged and re-plugged Sonos. Still receive the error message “Unable to browse music” from the Favorites button. If I go into “Recently Played” I am able to access a station that I played several days ago.

Then I’d certainly check with SiriusXM, who own the servers that feed your stream. 

This is not a SiriusXM issue. The same thing started happening with me today after installing the Sonos software update. All my favorites appear fine on the SiriusXM site. I’ve also tried rebooting the router and removing SiriusXM from Sonos and reinstalling it. Nothing.

Thanks everybody for the input. i agree with Brutz:

I’ve rebooted my router etc. My Favorites are showing up in SiriusXM app but not Sonos, and since Sonos posted this as a problem on their status page a few days ago I am guessing it never really got fixed, or at the very least the problem is back. If i have time today i will contact Sonos support.

This is still broken. And it’s not just Favorites. 

All of the Streaming channels (the numbers above 450-ish) are missing. For example, in the Sonos app, when hitting Browse → SiriusXM → Live Channels, the listing jumps from “SportsTalk” to “OtherPlayByPlay”. There should be a bunch of other categories (all the NHL, NFL, etc play-by-play categories, which are channels numbered in the 800’s and 900’s)

Still cannot browse music on my iPhone or iPad. I am having the same issue with anything above channel 470 as IndyVis has experienced.  Very frustrating! Not sure why we cannot access Sonos support on weekends.

I am only having the issue with Favorites in SiriusXM.  If I go to all Channels I can see everything.  So why can’t Favorites be read?

I have restarted my cable router, eero and still cannot read Favorites on PC controller, IPhone app or Android app.

Sonos is aware of the problem and is currently investigating it:

https://status.sonos.com/

And is now fixed.

i am so grateful! Many thanks to Louie from Sonos who stuck with me for 1 ½ hours attempting to identify the source of the glitch and find a solution to the problem!

Indeed! And thanks to everyone on this forum who raised the issue. It helped to know others were experiencing the same problem. So glad it’s all fixed.