Hi. I'm starting an App that needs an payment method, so I choosed to use PayPal Mobile Sample to test how it works but I'm having problems with the "Simple Payment" function

When I open the SimplePaymentOnClick Client Action this is the logic: 

Testing this exemple I noticed that the SimplePaymentOnClick don't call the StartSinglePaymentUI, because this Client Action never returned any error, even when I forced this error message in the StartSinglePaymentUI to appear in the App.

Can anyone tell me if have already used this Plugin, and how?

Bst Regards