Help to interactively troubleshoot a javascript problem with Woocommerce Paypal Advanced Credit Card

The WooCommerce JavaScript responsible for toggling the payment methods isn't running, or it's encountering a JavaScript error before it reaches the code that changes: .payment_box display: none; to .payment_box display: block; I can give you the URL of a page with an order ready to be paid. To access the payment page you will enter the email used to activate the order. The page briefly shown the "Pay now" button, then it disappears. When I toggle the payment methods, the relevant elements (pay now buttons/credit card form) are not shown/hidden as expected.