PayPal Express Checkout on Shopify keep fail to receive payment. Error code 10486
I have an online store build on Shopify. I'm having a problem of receiving payment by PayPal Express Checkout. Since we opened the online store, we can only received 1 transaction successfully. And all other transaction are fail and returned an error code 10486, with message "This transaction couldn't be completed. Please redirect your customer to PayPal." Our customer eventually have to abandon the order, and we are losing sales. Am I missing some setting on PayPal to make it work? Any hints?