Pandora on our player has stopped working as well.

Same problem. Pandora works fine but we get the same message...and just saw there is a system outage for Pandora on the Sonos status page.

Hi folks, thank you for reaching out to the Sonos community. We have identified a problem with Pandora on Sonos and are working with them on a fix. You may be unable to start playing music on your Sonos until it’s resolved.  You may check the status of the issue if has been fixed. If you need help with any other information, please be sure to let us know.