when there is no response back from the gateway, it means that the API information was rejected completely.
The API information is basically used as a login to the gateways server, on failed login, it sends the failure message and nothing else.
make sure that the API Username, API Password and API signature you are entering are correct.
the API Username is not the same as the email address, it will not contain an "@" symbol.
sometimes, paypal will generate bad api credentials, if you still have problems, try requesting new api credentials.
There are 2 stages to the checkout, when the confirm page posts to the paypal server, it is just authorizing the sellers account, at this stage, the cart information is not transferred.
the user will go through payapl and be brought back to your site to the pp_confirm page, at this stage, when the click the submit order button, the cart information will transferred to payapl.
Power tore Offers support for PayPal Express and Paypal Payments pro.
Paypal Payments Pro is a bundle of two services:
PayPal Direct payments and PayPal Express