My ecommerce system is Magento and had Paypal payments pro plug-in. I already got Credential from Paypal and filled some information such as API Username, API Password and API signature in my system. When I tried to checkout with credit card on my page, I got the "PayPal gateway has rejected request. This transaction cannot be processed. The merchant's account is not able to process transactions (#10548: Invalid Configuration)." error message.
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