Can't add visa test card using apple sandbox tester account

I'm integrating Applepay on web using braintree and apple Sandbox tester APPLE ID. I can't add a a test visa card. But can add a chinaUnionPay test card, but even with chinaUnionPay test card, I can't pay, I got the error:Error validating merchant:BraintreeError: Make sure you have registered your domain name in the Braintree Control Panel.


I reached out to brainTree support, turns out they can process test payment in my site using test visa card from APPLE. So the code is fine, only problem seems to be my sandbox test account or the fact that I'm in China?


I registered a new sandbox tester account and retry, still get the same error, and still can't add a visa test card.


Then I used a vpn to fake I'm in US, and set my iphone 6s to region: US and set my timezone to US, didn't help at all.


The test link: https://applepay.hqshop.net/Home/Join/testApple1


Can anyone help me?