Try removing the association with your Apple account from the system where it's missing. Close the controller, and then re-open it, and add the Apple account back in to it.
That should force a "re-sync" of all of the data. If it's still missing, I would recommend that you
submit a system diagnostic, and either post the number here, or
contact Sonos Support to discuss it. I tend to suggest the phone folks, they have more tools available, but are only available during business hours. Both the Twitter and Facebook support folks are available 24/7.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
