Azure AD Password Protection Help !

So we have had the above deployed (and successfully blocking passwords) since private preview and since updated code to public preview. We were eagerly awaiting the custom password list however having added a password to the list in Azure it does not appear to be working. We can see events suggesting the Proxy service is contacting Azure and getting a response (checking for the list?). We are wondering if it's a licencing problem as have seen conflicting info on this. We have E3 + EMS SKU for our users so have Azure AD Premium P1 I believe. Private preview doc said P2 required for custom password list but we have since read that you just need Azure AD Premium and actually that is for the Hybrid support and not the password list per se. Any clarification much appreciated !