PrestaShop errors can be caused by modules, themes, PHP versions, cache, database problems, permissions, or server configuration. The safest approach is to identify the exact error before changing anything.

1. Enable Debug Mode

If your PrestaShop website shows a blank page or generic error, enable Debug Mode temporarily.

Go to:

Back Office → Advanced Parameters → Performance → Debug Mode

Enable it and reload the page.

You may see a detailed error such as:

Class not found
Call to undefined method
SQLSTATE error
Permission denied
Memory limit exceeded

This is much more useful than a generic 500 Internal Server Error.

Important: Disable Debug Mode after troubleshooting because it can expose sensitive technical information to visitors.

2. Clear PrestaShop Cache

Cache problems can cause:

• Blank pages
• Old content
• Theme problems
• Module errors
• CSS/JavaScript problems

Go to:

Advanced Parameters → Performance → Clear Cache

Then reload your website.

If you’re using a CDN, server cache, or caching module, clear those caches too.

3. Common 500 Internal Server Error

A 500 error usually indicates a server-side problem.

Possible causes include:

• PHP error
• Incompatible module
• Theme problem
• Incorrect .htaccess
• PHP version incompatibility
• File permissions
• Insufficient memory
• Broken override

What to check

First check:

Hosting → Error Logs

Look for the error generated at the exact time you accessed the page.

For example:

PHP Fatal error
Allowed memory size exhausted
Call to undefined method
Class not found

The error log usually tells you where to start.

4. Blank White Page

A completely blank page is often caused by a PHP fatal error.

Try:

1. Enable Debug Mode.
2. Clear PrestaShop cache.
3. Check the server’s PHP error log.
4. Check recently installed/updated modules.
5. Check your theme.
6. Check PHP compatibility.

If the problem started immediately after installing a module, temporarily disable that module and test again.

5. Module Causing an Error

If the error appeared after installing or updating a module:

Back Office → Modules → Module Manager

Find the module and:

• Disable it.
• Clear cache.
• Test the website.

If the site becomes normal again, the module is likely involved.

Don’t immediately delete the module—first make sure you have a backup and understand whether it has database/configuration data that needs to be removed properly.

6. Theme Problems

A theme can cause errors after:

• PrestaShop upgrades
• PHP upgrades
• Theme updates
• Module updates

Check whether the problem disappears when using a compatible default PrestaShop theme.

If the default theme works but your custom theme doesn’t, investigate:

• Theme compatibility
• Custom overrides
• Template modifications
• JavaScript errors
• CSS issues

7. Database Errors

You might see errors such as:

SQLSTATE
Table doesn't exist
Unknown column
Database connection failed

First check your database connection settings.

For many PrestaShop installations, these settings are stored in:

/app/config/parameters.php

Older/newer versions can use different configuration structures, so don’t overwrite configuration files blindly.

Also check your hosting’s MySQL/MariaDB service status.

Always back up the database before making database changes.

8. “Unable to Connect to Database”

Possible causes:

• Incorrect database hostname
• Incorrect database username/password
• Database server unavailable
• Database deleted or corrupted
• Hosting configuration changed

Check your database credentials and confirm that the database server is running.

9. 404 Page Not Found

If product or category URLs suddenly return 404 errors:

Go to:

Shop Parameters → Traffic & SEO

Check your URL settings.

Then regenerate .htaccess by saving the URL configuration again, if appropriate for your PrestaShop version.

Also check:

• Product enabled status
• Category status
• SEO URLs
• URL rewriting
• Recent migrations or upgrades

10. Images Not Displaying

If product images disappear, check:

File permissions

Make sure the web server can read the image directories.

Image regeneration

Go to:

Design → Image Settings

You can regenerate thumbnails if the image types or dimensions have changed.

Be careful with regeneration on a large store because it can consume considerable server resources.

11. Checkout or Payment Problems

If customers can browse products but can’t complete checkout, check:

• Payment module status
• Payment gateway credentials
• SSL/HTTPS
• Currency configuration
• Country restrictions
• Tax rules
• Shipping methods
• Carrier availability
• Required customer fields

Perform a test order after making changes.

For payment problems, also check the payment provider’s logs/dashboard.

12. Emails Not Sending

If customers aren’t receiving order confirmation emails:

Check:

Advanced Parameters → E-mail

Verify the configured mail method and SMTP settings.

Also check:

• SMTP username/password
• SMTP port
• Encryption
• Sender email
• Hosting mail restrictions
• Spam/junk folder

For reliable ecommerce email delivery, an authenticated SMTP service is generally preferable to relying on basic PHP mail.

13. Slow PrestaShop Website

A slow store can be caused by:

• Too many modules
• Large images
• Slow hosting
• Database problems
• Poorly optimized theme
• Excessive JavaScript/CSS
• Disabled caching
• External scripts
• Large catalog/database

Start by identifying the slow component rather than randomly disabling features.

Check:

Advanced Parameters → Performance

Review caching and optimization settings appropriate to your PrestaShop version.

14. “Permission Denied” Errors

Incorrect file permissions can prevent PrestaShop from reading or writing files.

Check permissions through your hosting control panel or SSH.

Avoid setting everything to 777. That can create security problems.

Use the permissions recommended by your hosting environment and PrestaShop version.

15. Error After PrestaShop Upgrade

If an error appears immediately after upgrading:

Check these first:

1. Third-party modules
2. Custom theme
3. Overrides
4. PHP version
5. PHP extensions
6. Cache
7. Server error logs

If the upgrade cannot be completed or the store is seriously broken, don’t keep making random changes.

Restore the backup/staging environment and investigate the specific compatibility problem.

Quick Troubleshooting Table

Best Troubleshooting Process

Use this order instead of changing many things at once:

1. Identify the exact error → 2. Check logs → 3. Enable Debug Mode → 4. Clear cache → 5. Check recent changes → 6. Test modules/theme → 7. Check PHP/server → 8. Make one change at a time → 9. Test again → 10. Restore backup if necessary.

Before making major changes

Always take a complete backup of your PrestaShop files and database.

This makes troubleshooting much safer because you can return to the previous working state if a change makes the problem worse.