Payment button returns "Nothing Found"

We are using Braintree payment gateway, after setting up the Braintree account, we tested out, after submitted the credit card info, we saw the error message “Nothing Found… This is something embarrassing, isn’t it?…”

After reading the forum postings, we went to the Page & Button Links, set up Callback = Payment Callback (This page we set up using the Payment Callback template). After testing, still the same.

Please help!!

Thanks.