Yeah - it's 10501. According to PayPal's API Error Codes page this means:
10501 Invalid Configuration - This transaction cannot be processed due to an invalid merchant configuration. Occurs when the billing agreement is disabled or inactive.
I'm convinced that PayPal's sandbox system is wonky. The seller account is definitely set up properly. Anyhow I'm going to continue my development - which centers around Gravity Forms as the payment mechanism - and try it with a production account later on.
PS - The error codes are displayed as an HTML comment immediately prior to the error message in the credit card field as per code in paypalprop.php:
$message = __("<!-- Payment Error: " . $code . " -->There was an error processing your request. Your credit card was not charged. Please try again.", "gravityforms");
Posted 11 years ago on Thursday August 23, 2012 | Permalink