When a Shopify checkout stops working, check four things in order: the payment provider settings, apps or scripts that touch the cart and checkout, the custom domain connection, and any checkout customisations. Shopify itself rarely goes down, so the cause is usually something added to your store.
1. Payments
In Settings, then Payments, check your provider is active, verified and not asking for more information. A paused Shopify Payments account stops checkout.
2. Apps and scripts
Upsell, currency, cart and discount apps often break the checkout after an update. Disable recently added or updated apps one at a time and test.
3. The domain
If the checkout works on your myshopify.com address but not your own domain, the domain's DNS or certificate is the problem. Check Settings, then Domains.
4. Checkout settings
Required fields, shipping zones with no rates, or markets with no payment method can all stop customers finishing an order.
We test as a customer, find the cause and fix it: checkout and payment repairs.
