What this problem looks like
WooCommerce checkout depends on AJAX updates, PHP sessions, and often third-party payment iframes. When any layer breaks, customers see endless loading or a form that submits but creates no order.
Most checkout failures are not payment gateway bugs on day one. They are minified JavaScript errors, full-page cache serving stale cart data, or a security plugin blocking REST requests to wp-json.
Step 1: Confirm what customers actually see
Ask for a screenshot or screen recording. Checkout can fail at three different points: loading the page, updating shipping or totals, or placing the order. Each points to a different layer.
Test as a guest and as a logged-in customer. If only guests fail, look at cookie consent banners or caching that treats anonymous users differently.
- Blank checkout page: PHP fatal or theme template conflict.
- Spinner on Place Order: JavaScript error or blocked AJAX.
- Order created but no payment: gateway configuration issue.
Step 2: Enable WooCommerce logging and WP debug
Turn on logging under WooCommerce → Settings → Advanced → Logs. Choose a log source such as fatal-errors or a payment gateway, then reproduce the failure and download the log file.
Open wp-config.php in your site root, next to wp-admin and wp-content. Search for existing WP_DEBUG constants before adding duplicates:
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );Step 3: Exclude checkout from cache and CDN
Never cache cart, checkout, or my-account pages. LiteSpeed, WP Rocket, W3 Total Cache, and Cloudflare APO all need explicit exclusions. Cached checkout often shows wrong totals or stale nonces that break Place Order.
- Add
/cart/,/checkout/, and/my-account/to do-not-cache rules. - Purge all cache after changing exclusions.
- Disable Rocket Loader or similar JavaScript optimisers on checkout as a test.
Step 4: Check SSL, cookies, and mixed content
Payment fields require HTTPS. If siteurl and home still use http, or assets load over http, browsers block card fields. Confirm both WordPress URLs use https and that your certificate covers www and apex.
Cookie paths must match your domain. Staging copies with wrong URLs in the database break sessions when copied to production without search-replace.
Step 5: Isolate plugin and theme conflicts
Rename wp-content/plugins to plugins.disabled via File Manager, SFTP, or FTP. If checkout works, rename the folder back to plugins and activate plugins one at a time in wp-admin until the checkout error returns.
Switch to Storefront for thirty minutes. If checkout works, the active theme or a plugin template override is the cause.
When to stop DIY and hire help
Hire a WooCommerce developer if checkout still fails with a default theme, if logs show core WooCommerce fatals, or if you run a high-volume shop and cannot afford trial-and-error during trading hours. BugShield fixes checkout errors at a confirmed price without hourly billing surprises.