If you are using PayFlow Pro (Direct Payments on your website), you don't need to configure anything in the PayPal Manager.  However, if you are using the PayFlow Link (Hosted Payment Page), see the settings below.  Also, Make sure you are using PDshop version 10.038 or higher, earlier versions do not support Hosted Checkout Pages or PayFlow Pro.

In your PayPal Manager, navigate to Service Settings > Hosted Checkout Pages > Set Up

Under Display options on payment page:

Enter Cancel URL:
https:// your domain /shop/gateway_cancel.aspx

Enter Error URL: Leave Blank

Cancel URL Method: Get

Under Payment Confirmation:

Show confirmation page: On my website

Enter Return URL:
https:// your domain /shop/gateway_in.aspx

Return URL Method: Get

Silent Post for Data Transfer
Use Silent Post: Yes

Enter Silent Post URL:
https:// your domain /shop/gateway_ppipn.aspx

Return URL when Silent Post fails: Blank

Security Options
Enable Secure Token: Yes