Paypal Express checkout question

I have a newly setup ecommerce site
And I have all API setting inputted to the paypal express check out extension, then I tried to check out which everything is fine (successfully linked to paypal, inputted credit card number and information)

but it shows this from paypal
"Sorry, we can’t complete your purchase at this time
Please return to the merchant and choose another way to pay."

I think it might be my IPN URL is not right?
this is my link
http://www.mysite.com/index.php?route=e ... xpress/ipn

but I have no idea how to check if this link is correct.

ANYONE CAN HELP / . \