Why is a payment method (Shop Pay / PayPal / Apple Pay) missing at checkout?

A payment method disappears when it’s restricted by country, currency or customer rules, the express wallet (Apple Pay / Google Pay) needs domain verification, the gateway isn’t activated for that market, or a payment customization Function is hiding/reordering it. Shop Pay also needs the customer accounts and the right activation. We check each condition against a real test checkout to see exactly why it’s not rendering.