Have you tried removing Pandora from your Sonos account and adding it again?

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We’re having the same problem--also started 2 days ago. Sometimes get ‘access denied’ and sometimes works. Pandora account is fine (can listen via browser, for example).

So, if the option suggested by GuitarSuperstar above doesn’t work for you, I’d certainly try a network refresh, by unplugging all Sonos devices. While they are unplugged, reboot the router. Once the router comes back up, plug back in all Sonos devices. 

However, if neither of those two options work, and the network status page doesn’t show the service as being down, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, there are more options available beyond just the diagnostic analysis.

Thank u guitarsuperstar.  That worked!!

Same issue occurring for me. 

Removing the Pandora service and adding it back has appeared to solve the problem for us. 

I have reauthorized my Pandora through the Sonos app and it corrected it. 

Reauthorizing isn’t working for me. Pandora says it doesn’t even know my email

Same issue. Sometimes it works, sometimes I have to reauthorize the Pandora account, sometimes I have to remove and re-add the account. It’s very annoying. 

I’ve been having this trouble for months and have not used pandora. It’s amazing how amazon and apple work. Well, amazon did deny me one time but I reauthorized and its worked for the last year. Today I spent 30 minutes trouble shooting and it finally works. Signed out, deleted app, reauthorized, emailed sonos support with my frustration. Good luck! It seems everyone one wants data, money for each service on top of platform services, your first born child and more!