How to setup credit card payment in JD PayPal Pro

Dear JD team,

I've installed the Paypal pro plugin in Joom donation. I got the Paypal classic API credentials from my paypal account and entered them into the plugin's parameters. In the donation form, when I choose the Paypal pro payment method, the credit card number box and related fields appears. But after filling in these and click "Process donation", I get a blank page.

Is there any other configuration needed? How can I figure out what happen?

Thank you in advance,
Wai