"PayPal Payments Advanced Demo" - Hosted Checkout failed with Code 12

[himalpatel]

I'm using sample application "Paypal Payments Advanced Demo" with hosted checkout. When I test a sale/authorize transaction it fails with result code 12. no other error message. I make sure that i'm using proper credit card detail of the personnel account. 

What else i should look for ?

Thanks in advance!

Himal