I just tried to use the Express Checkout Wizard from Paypal, but, after 1 hour, I didn’t had any success. All the time I get the same error:
GetExpressCheckoutDetails API call failed.
Detailed Error Message: PaymentAction : Required parameter missing
Short Error Message: Missing Parameter
Error Code: 81115
Error Severity Code: Error
Looking where the Payment action is “hidding” I found the following mistake on paypalfunctions.php code
$token = urlencode($_SESSION['token']);
$paymentType = urlencode($_SESSION['paymentType']);
$token = urlencode($_SESSION['TOKEN']);
$paymentType = urlencode($_SESSION['PaymentType']);
And this solved my problem.
I hope this will help you.