Fix WooCommerce Cart & Checkout

My WooCommerce site suddenly refuses to let customers add items to the cart, log into their accounts, or complete a purchase. The issue appears on every device and browser I’ve tried, and I haven’t touched any themes, plugins, or other settings recently. Because nothing else has changed, I strongly suspect that a caching layer—whether it’s a plugin, server-side object cache, or CDN page cache—is interfering with the session/nonce logic WooCommerce relies on.

Here’s what I need from you:

• Diagnose the exact conflict or misconfiguration that is blocking add-to-cart, login, and checkout actions.
• Apply the fix (or safe workaround) so those three functions work smoothly again.
• Confirm the solution across multiple browsers in an incognito/private window to be sure cached assets aren’t masking the result.
• Provide a brief summary of what was wrong and the steps you took, so I can avoid a recurrence after future updates.

You’ll have full WordPress admin and cPanel access on a staging clone first, then production once we’re confident everything is stable. If you prefer specific tools (Query Monitor, Debug Bar, WP-CLI, etc.) just let me know so I can enable them.

The job is finished when customers can add products to the cart, log in, and check out without errors or page reload loops.