Integrating Paypal Test account in asp.net mvc

Question

I have developed a simple asp.net application and added paypal payment method.

 

<add key="business" value="[email protected]" />
<add key="isSandbox" value="true" />
<add key="currency_code" value="USD" />
<add key="return" value="http://localhost/PayPal/RedirectFromPaypal" />
<add key="cancel_return" value="http://localhost/PayPal/CancelFromPaypal" />
<add key="notify_url" value="http://localhost/PayPal/NotifyFromPaypal" />

<add key="test_url" value="https://www.sandbox.paypal.com/cgi-bin/webscr" />
<add key="Prod_url" value="https://www.paypal.com/cgi-bin/webscr" />

 

But i am getting the error:

 

We cannot process this transaction because there is a problem with the PayPal email address supplied by the seller. Please contact the seller to resolve the problem. If this payment is for an eBay listing, you can contact the seller via the "Ask Seller a Question" link on the listing page. When you have the correct email address, payment can be made at www.paypal.com. 

 I think my business test account is verified but still getting the error??

what should i do?