WooCommerce checkout broken after a plugin update: what I check first

I get this one a lot. Yesterday the store was taking orders. Today the checkout button does nothing, or you get a blank page, or a vague "Something went wrong" message. Nine times out of ten it is not mysterious. Something changed, usually a plugin or WordPress update, and checkout is the first place that shows it.

Here is how I usually chase it down without making things worse.

Do not keep clicking "update all"

If checkout just broke, more updates are the wrong next step. You want a calm rollback path first. Note what changed in the last day: WooCommerce, payment gateway, caching, security, page builder, PHP version. That short list is your suspect sheet.

Check the obvious blockers

• Caching or a CDN serving a stale checkout page
• A payment plugin that updated overnight
• A conflict between WooCommerce and a "performance" or "security" plugin
• JavaScript errors in the browser console on the checkout page
• PHP errors in the server log right when you hit Place order

Reproduce it cleanly

Open checkout in a private window. Disable browser extensions. Try as a guest and as a logged-in customer. If it only fails for guests, look at sessions, cookies, and caching rules that treat /checkout as cacheable when it should not be.

Isolate plugins safely

On staging if you have it. If you only have production, do the smallest test you can: switch to a default theme briefly, or disable non-essential plugins one group at a time. Start with anything that touches scripts, security headers, or "optimise JS". Payment and WooCommerce core stay on until you have a reason to touch them.

Read the error instead of guessing

Browser console for JS. WooCommerce logs for gateway responses. Server error log for fatal PHP. A fatal in a shipping calculator or a gateway callback is more common than people think, and the UI often hides the real message.

When to call someone in

If you have already spent an hour swapping plugins with no clear signal, stop. Checkout downtime costs money. I have a short write-up of the usual failure patterns here: WooCommerce checkout not working.

Fix the actual error, then update on staging next time. That boring habit saves more weekends than any "optimisation" plugin ever has.