PrestaShop Orders and Cart — Analysis of 734 Interventions Since 2018

Is your PrestaShop store experiencing order or cart problems? Customers can't complete their purchases, orders are stuck, the cart empties for no reason, or invoices aren't generating? You're not alone. Since 2018, MonSiteBug has resolved 734 order and cart-related tickets on PrestaShop — the second most common issue after technical errors.

This article is an exclusive study based on our real data. No forum copy-paste: hard numbers from our 8,660 support tickets, root causes identified in the field, and solutions that actually unblocked the checkout process for our clients.

PrestaShop order and cart problems in numbers: 2018-2026

The checkout funnel is the heart of your online store. Everything converges to this point: the customer found their product, added it to the cart, and is about to pay. If the process crashes at this stage, it's a lost sale — and often a permanently lost customer. Here's the evolution:

Observation: 2023 marks the peak with 124 tickets. PrestaShop 8 migrations triggered a wave of checkout problems: incompatible cart modules, broken price rules, incorrect VAT calculations post-migration. Volume remains high in 2025 (111 tickets) with PrestaShop 9 deeply modifying the native order process.

Breakdown by issue type

Order and cart problems span a wide spectrum. Here's the real breakdown of our 734 interventions:

Order problems: 405 tickets analyzed

More than half of our interventions concern the order process itself. Here are the most frequent causes:

1. Checkout crash (error 500 or blank page)

The most critical scenario: the customer clicks "Order" and gets a 500 error or blank page. Main causes:

• Incompatible checkout module: third-party One Page Checkout modules can conflict with payment or shipping modules
• Conflict between payment and shipping modules: a shipping module that modifies the cart during the payment process
• Defective price rules: a misconfigured cart rule causing a calculation error
• Corrupted controller override: an override of OrderController or CartController containing a PHP error

2. Order stuck in "Awaiting payment"

The customer paid (money is debited), but the order stays "Awaiting payment" in the back-office. This is directly linked to payment problems we've analyzed: the payment module's webhook/IPN isn't working properly, and PrestaShop is never informed that payment was accepted.

3. Duplicate orders

A customer places one order, but two (or more) appear in the back-office. This bug is often caused by:

• Double-clicking the "Order" button: if the button isn't disabled after the first click
• Payment module timeout: the customer goes back and restarts the process
• Checkout module submitting the form twice: JavaScript bug in the module

4. Price rules and promotions breaking checkout

Cart rules and promotions are a frequent source of bugs:

• Promo code making total negative: PrestaShop refuses the order if total is <= 0
• Free shipping not applying: cart rule conditions misconfigured
• Discount applying to wrong product: conflict between multiple price rules
• VAT miscalculated after coupon: known bug on certain PrestaShop versions

Cart problems: 291 tickets analyzed

The cart is the first step of the order funnel. If it doesn't work, no order will ever be placed.

1. "Add to cart" button not working

The most frequent cart problem. The customer clicks "Add to cart" and nothing happens. Causes:

• JavaScript error: a conflict between the theme and a module blocks the add-to-cart JavaScript event
• Misconfigured product: no combination selected for a product with attributes, stock at 0, disabled product
• Browser or server cache: a cached version of the page prevents interaction
• Custom product module: a module that modifies the product page and breaks the add-to-cart form

2. Cart emptying itself

The customer adds products, navigates to other pages, and when they return to the cart — it's empty. This is often linked to:

• Cookie configuration: cookie lifetime too short, or domain issue (www vs non-www)
• PHP session expiring: the server's session.gc_maxlifetime is too short
• Aggressive cache module: a cache module caching the cart page (which should never happen)
• Partial SSL/HTTPS: the site is HTTP on some pages and HTTPS on others, creating two different sessions

3. Incorrect cart calculations

The cart shows an incorrect amount: miscalculated VAT, wrong shipping costs, discount not applied or applied twice. These bugs are particularly common after a PrestaShop version migration or checkout module change.

Module conflicts: the #1 root cause

In the vast majority of our 734 interventions, the root cause is a module conflict. The PrestaShop checkout funnel involves many hooks and modules simultaneously:

When two modules try to modify the same element at the same time (cart amount, shipping costs, validation process), unpredictable bugs appear. That's why we recommend exhaustively testing the checkout funnel after every module installation or update.

How to diagnose a PrestaShop order/cart problem

Here's the methodology we apply, refined through our 734 interventions:

1. Reproduce the problem

Add a product to the cart and follow the complete order funnel. Note at which exact step the problem appears: add to cart, cart page, shipping choice, payment choice, or confirmation.

2. Check the JavaScript console

Open developer tools (F12) and watch the JavaScript console and Network tab throughout the entire process. The majority of cart bugs are caused by JavaScript errors that prevent AJAX requests from completing.

3. Disable third-party checkout modules

If you use a One Page Checkout module or any module that modifies the order funnel, temporarily disable it and test with the native PrestaShop checkout. If the problem disappears, the third-party module is the cause.

4. Check overrides

Review the /override/ folder. If files override checkout-related controllers (CartController, OrderController, PaymentModule), they could be the source. Temporarily rename them to test.

5. Check logs

Review PHP logs and PrestaShop logs (var/logs/). Cart calculation errors, stock issues, and module errors are detailed there.

Solutions and best practices

For checkout

• Use a reliable, maintained One Page Checkout module compatible with your PrestaShop version
• Test the complete order funnel after every module update
• Disable the "Order" button after the first click to prevent duplicates
• Keep a minimal number of active modules on checkout pages

For cart

• Force HTTPS on all pages (no HTTP/HTTPS mix)
• Increase PHP session lifetime (at least 1800 seconds)
• Never cache cart and checkout pages
• Check cookie configuration (consistent www/non-www domain)

For orders

• Regularly check "Awaiting payment" orders — they often indicate a webhook problem
• Test each payment method after an update
• Set up alerts for orders stuck for more than 24 hours

Our order/cart numbers at a glance

Why trust us with your order problems?

Since 2018, we've resolved 734 order and cart problems on PrestaShop. Crashing checkout, emptying cart, stuck orders, missing invoices — we've seen every scenario. The checkout funnel is our primary area of expertise, alongside 500 errors and payment problems.

What sets us apart:

• 734 order/cart tickets resolved — checkout, cart, invoices, stock
• In-depth diagnosis — we analyze modules, overrides, hooks, and logs
• Resolution without data loss — existing orders are preserved
• Multi-module expertise — we know the classic conflicts between payment, shipping, and checkout modules
• 8,660 total tickets handled — comprehensive view of the PrestaShop ecosystem

Every minute your checkout is down, you're losing sales. Contact us for a quick diagnosis, or check our pricing for our intervention packages.

Need help now? Create a support ticket or contact us directly. Our team acts quickly to unblock your checkout funnel.