Direct Post
Append?preferred=crypto_coin to the checkout_url to skip the default payment page and take the payer straight to the crypto coin checkout:
{purchase_id} is the purchase ID from the checkout_url field returned in the purchase response. Use your own purchase’s ID — example URLs pointing at someone else’s purchase will not work.
Crypto Coin is a redirect method: no customer data entry is needed on the payment page, so ?preferred=crypto_coin takes the payer straight to the crypto checkout.
If you want to pre-select Crypto Coin on the default payment page while still showing the customer all available options, use ?active=crypto_coin instead.