Payment Plugin: BlueSnap
Up to date instructions can be found here
For BuyNow Hosted Payment Page You must set Data Protection Key within your BlueSnap account: CHECKOUT PAGE -> Payment Methods
Set IPN URL: Settings -> General Settings -> (Notifications)
https://example.com/amember/payment/bluesnap/ipn
For one-time products BlueSnap Contract ID is not required.
For auto-recurring products you need to create Contract with same billing cycle within your BlueSnap account and set its ID withih Product Settings in aMember: aMember CP -> Products -> Manage Products -> (edit) Field: BlueSnap Contract ID