My PIN says invalid when trying to add the Disney app

I assume you're speaking of the Parental Control that's set to require a PIN to add an app.  Can you add any app or is it only failing for that one?  What if you remove the PIN, add the app, and then set it up again?  After you remove the PIN, you may have to restart your Roku device for the change to take effect.

How to create, reset, or remove your Roku PIN | Official Roku Support