The Payment Settings have been updated in PBBooking 3.0.0 to use the new Paypal API. This means that if you have been using the previous payment settings with IPN you will need to turn the IPN off, as the functions listening for IPN events no longer exist.
To correctly setup Paypal you will require the following information from your Paypal Account.
Paypal API Username
Paypal API Password
Paypal API Signature
Your API Username, API Password & API Signature can be obtained from your Paypal Account. To access this, log in to your account and click Profile from the top menu bar. Then go to the My Selling Tools from the left side menu and click Update on the API access section of the page.
From the resulting page select Option 2. View API Signature. This will show your API details.