Overview

A WordPress JSON error (most commonly displayed as "The response is not a valid JSON response") typically occurs in the Gutenberg block editor, page builders, or WooCommerce cart/checkout pages. It means your browser expected formatted data from the server, but received something else—usually an unexpected PHP error, broken permalinks, or a blocked API endpoint.

Follow the step-by-step guide below to resolve this error on your Managed WordPress website.

Step-by-Step Troubleshooting Guide

1. Flush Your Permalinks & Clear Cache

Broken permalinks are the most common cause of JSON errors in WordPress.

1. Log into your WordPress Dashboard.

2. Go to Settings -> Permalinks.

3. Scroll to the bottom and click Save Changes (you do not need to change any settings—clicking Save flushes and rewrites your site’s permalink rules).

4. Clear your browser cache or re-test in an Incognito/Private window.

2. Verify Your Site URLs & SSL Settings

Mismatched site URLs cause REST API security blocks.

1. In your WordPress Dashboard, go to Settings -> General.

2. Ensure both WordPress Address (URL) and Site Address (URL) match exactly, including https://.

3. Check for Plugin and Theme Conflicts

Custom themes or ecommerce plugins can interfere with the WordPress REST API.

1. Go to Plugins > Installed Plugins and temporarily deactivate all plugins except core dependencies (like WooCommerce).

2. Test the action that caused the JSON error.

3. If the error resolves, reactivate your plugins one by one to identify the conflicting plugin.

4. If plugins are not the cause, temporarily switch to a default theme (like Twenty Twenty-Four or Storefront) under Appearance -> Themes to test if your active theme is the cause.

4. Regenerate Your .htaccess File in Plesk

Corrupt rewrite rules in your server configuration will break API requests (/wp-json/).

1. Log in to your hosting Plesk Control Panel.

2. Go to Websites & Domains -> select your domain -> File Manager.

3. Locate the .htaccess file inside your httpdocs folder.

4. Rename .htaccess to .htaccess_old.

5. Return to your WordPress Dashboard -> Settings -> Permalinks and click Save Changes to generate a fresh .htaccess file.

5. Check WordPress Site Health Status

1. Go to Tools -> Site Health in your WordPress dashboard.

2. Check the Status tab for specific REST API or loopback request errors. Note any HTTP status codes listed (e.g., 403 Forbidden or 500 Internal Server Error).

PHP Server Limit Adjustments (Requires Live Support)

Ecommerce platforms like WooCommerce require higher server limits to process REST API requests. If your server exhausts memory mid-request, it will return an HTML error page instead of JSON.

If you need to increase any of the following PHP directives beyond your panel defaults, please contact our support team:

• memory_limit (Recommended: 256M or 512M)

• max_execution_time (Recommended: 300)

• post_max_size / upload_max_filesize

Need Extra Help?

If you have completed these troubleshooting steps and are still experiencing JSON response errors, please reach out to our technical support team:

• Action: Connect directly with a Live Agent through this chat window.

• What to provide: Share your Domain Name, a full-screen screenshot of the error, and any details from your Site Health tool.

• Web Development & Advanced Troubleshooting: Because custom code, complex plugin conflicts, or custom database modifications fall outside the scope of server support, we strongly recommend hiring a web developer or a specialist with expertise in WordPress/WooCommerce if the issue is rooted in custom theme or code development.