Title: Critical Error Upon Installing/Activating Plugin
Last modified: April 29, 2025

---

# Critical Error Upon Installing/Activating Plugin

 *  Resolved [kgas1](https://wordpress.org/support/users/kgas1/)
 * (@kgas1)
 * [1 year, 1 month ago](https://wordpress.org/support/topic/critical-error-upon-installing-activating-plugin/)
 * Hello,
 * I have tried to install and activate this plugin and as soon as I activated it,
   a critical error instantly appeared and site was unusable until we went into 
   the backend to deactivate the plugin.
 * Going through the logs,
 * **Critical** Uncaught Error: Class “WooCommerce\Square\Admin\Product_Editor_Compatibility”
   not found in /www/theredheartcampaign_983/public/wp-content/plugins/woocommerce-
   square/woocommerce-square.php:455
 * **Critical** Uncaught Error: Class “WooCommerce\Square\Admin\Product_Editor_Compatibility”
   not found in /www/theredheartcampaign_983/public/wp-content/plugins/woocommerce-
   square/woocommerce-square.php:455 Additional context{ “error”: { “type”: 1, “
   file”: “/www/theredheartcampaign_983/public/wp-content/plugins/woocommerce-square/
   woocommerce-square.php”, “line”: 455 }, “remote-logging”: true, “backtrace”: [“”,“#
   0 /www/theredheartcampaign_983/public/wp-includes/class-wp-hook.php(324): WooCommerce_Square_Loader-
   >declare_features_compatibility(”)”, “#1 /www/theredheartcampaign_983/public/
   wp-includes/class-wp-hook.php(348): WP_Hook->apply_filters(NULL, Array)”, “#2/
   www/theredheartcampaign_983/public/wp-includes/plugin.php(517): WP_Hook->do_action(
   Array)”, “#3 /www/theredheartcampaign_983/public/wp-content/plugins/woocommerce/
   includes/class-woocommerce.php(841): do_action(‘before_woocomme…’)”, “#4 /www/
   theredheartcampaign_983/public/wp-includes/class-wp-hook.php(324): WooCommerce-
   >init(”)”, “#5 /www/theredheartcampaign_983/public/wp-includes/class-wp-hook.
   php(348): WP_Hook->apply_filters(NULL, Array)”, “#6 /www/theredheartcampaign_983/
   public/wp-includes/plugin.php(517): WP_Hook->do_action(Array)”, “#7 /www/theredheartcampaign_983/
   public/wp-settings.php(704): do_action(‘init’)”, “#8 /www/theredheartcampaign_983/
   public/wp-config.php(106): require_once(‘/www/theredhear…’)”, “#9 /www/theredheartcampaign_983/
   public/wp-load.php(50): require_once(‘/www/theredhear…’)”, “#10 /www/theredheartcampaign_983/
   public/wp-blog-header.php(13): require_once(‘/www/theredhear…’)”, “#11 /www/theredheartcampaign_983/
   public/index.php(17): require(‘/www/theredhear…’)”, “#12 {main}”, “thrown” ] }
 * We need to get this plugin installed in order to be able to take payments through
   Square. Any thoughts/insights would be greatly appreciated.
 * The page I need help with: _[[log in](https://login.wordpress.org/?redirect_to=https%3A%2F%2Fwordpress.org%2Fsupport%2Ftopic%2Fcritical-error-upon-installing-activating-plugin%2F%3Foutput_format%3Dmd&locale=en_US)
   to see the link]_

Viewing 2 replies - 1 through 2 (of 2 total)

 *  [Mahfuzur Rahman](https://wordpress.org/support/users/mahfuzurwp/)
 * (@mahfuzurwp)
 * [1 year, 1 month ago](https://wordpress.org/support/topic/critical-error-upon-installing-activating-plugin/#post-18442950)
 * Hi [@kgas1](https://wordpress.org/support/users/kgas1/),
 * Thanks for sharing those details.
 * The error you’re seeing usually means that the plugin is trying to load a class
   that’s missing or not being included correctly. This can happen if the plugin
   didn’t install fully, if a file is inaccessible, or if there’s a conflict with
   another plugin or your theme.
 * Here’s what I recommend:
    1. **Delete the current WooCommerce Square plugin** from your site.
    2. **Download a fresh copy** directly from [https://wordpress.org/plugins/woocommerce-square/](https://wordpress.org/plugins/woocommerce-square/)
    3. **Reinstall and activate the plugin**.
    4. Make sure you’re using the latest versions of WordPress, WooCommerce, and PHP.
 * Let us know how it goes!
 *  Plugin Support [Kay U a11n](https://wordpress.org/support/users/kingsleyinfo/)
 * (@kingsleyinfo)
 * [1 year, 1 month ago](https://wordpress.org/support/topic/critical-error-upon-installing-activating-plugin/#post-18457397)
 * We haven’t heard back from you in a while, so I’m going to mark this as resolved.
 * If you have a few minutes, we’d love if you could leave us a review: [https://wordpress.org/support/plugin/woocommerce/reviews/](https://wordpress.org/support/plugin/woocommerce/reviews/)

Viewing 2 replies - 1 through 2 (of 2 total)

The topic ‘Critical Error Upon Installing/Activating Plugin’ is closed to new replies.

 * ![](https://ps.w.org/woocommerce-square/assets/icon-256x256.png?rev=3234354)
 * [WooCommerce Square](https://wordpress.org/plugins/woocommerce-square/)
 * [Frequently Asked Questions](https://wordpress.org/plugins/woocommerce-square/#faq)
 * [Support Threads](https://wordpress.org/support/plugin/woocommerce-square/)
 * [Active Topics](https://wordpress.org/support/plugin/woocommerce-square/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/woocommerce-square/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/woocommerce-square/reviews/)

 * 2 replies
 * 3 participants
 * Last reply from: [Kay U a11n](https://wordpress.org/support/users/kingsleyinfo/)
 * Last activity: [1 year, 1 month ago](https://wordpress.org/support/topic/critical-error-upon-installing-activating-plugin/#post-18457397)
 * Status: resolved