如何在PayPal中實現自適應付款

我想在我的網站中實施自適應付款。我努力，但得到一個錯誤下面是我的代碼如何在PayPal中實現自適應付款

<html> 
<head> 
<script src="https://www.paypalobjects.com/js/external/dg.js" type="text/javascript"></script> 
</head> 

<body> 
<form action="https://www.sandbox.paypal.com/webapps/adaptivepayment/flow/pay" target="PPDGFrame" class="standard"> 
<label for="buy">Buy Now:</label> 
<input type="image" id="submitBtn" value="Pay with PayPal" src="https://www.paypalobjects.com/en_US/i/btn/btn_paynowCC_LG.gif"> 
<input id="type" type="hidden" name="expType" value="light"> 
<input id="paykey" type="hidden" name="paykey" value="APP-80W284485P519543T"> 
</form> 

<script type="text/javascript" charset="utf-8"> 
var embeddedPPFlow = new PAYPAL.apps.DGFlow({trigger: 'submitBtn'}); 
</script> 
</body> 

</html>

，而我對Pay Now按鈕，點擊會收到以下錯誤

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