Why can't I use my PayPal credit card for Onsite payments?

Our API Payment process is called Adaptive Payments and does not support PayPal Smart Connect (or PayPal Credit) with our setup at this time. You can still send money using PayPal credit if you send it through their site directly, but unfortunately at this time it will not work through BrickLink's onsite payment. We do have plans to make the payment status for onsite more flexible in the future, but for now please send payment through PayPal directly if you need to use your PayPal credit card.