magento2 Braintree payment如何使用？

Question

https://www.braintreepayments...
从这里注册了个sandbox account，然后到magento EE 2.0.10后台开启了Braintree，并输入了sandbox提示的key，在CHECKOUT时会显示信用卡输入，但我使用多张测试卡，它仍然提示失败。

我查LOG，会得到以下信息：

exception 'Braintree_Exception_Authorization' in /home/mg2e1dem/public_html/vendor/braintree/braintree_php/lib/Braintree/Util.php:56
#0 /home/mg2e1dem/public_html/vendor/braintree/braintree_php/lib/Braintree/Http.php(44): Braintree_Util::throwStatusCodeException(403)
#1 /home/mg2e1dem/public_html/vendor/braintree/braintree_php/lib/Braintree/TransactionGateway.php(392): Braintree_Http->post('/merchants/wz22...', Array)
#2 /home/mg2e1dem/public_html/vendor/braintree/braintree_php/lib/Braintree/TransactionGateway.php(45): Braintree_TransactionGateway->_doCreate('/transactions', Array)
#3 /home/mg2e1dem/public_html/vendor/braintree/braintree_php/lib/Braintree/TransactionGateway.php(240): Braintree_TransactionGateway->create(Array)
#4 /home/mg2e1dem/public_html/vendor/braintree/braintree_php/lib/Braintree/Transaction.php(450): Braintree_TransactionGateway->sale(Array)
#5 /home/mg2e1dem/public_html/vendor/magento/module-braintree/Model/Adapter/BraintreeTransaction.php(25): Braintree_Transaction::sale(Array)

查代码是因为返回了403，但我的KEYS反复验证过没有错，而且也换了一个新的，仍然不行。

我的测试卡从以下地址获取：
https://developers.braintreep...