WooCommerce as Must-Use plugin

This plugin does not support WooCommerce as a MU-plugin, which means all product review functionality is disabled in this plugin.

To fix this issue replace the check for WooCommerce being active using
is_plugin_active( 'woocommerce/woocommerce.php' ) with
class_exists( 'woocommerce' ).
Both functions return the same boolean result, but class_exists will also work for mu-plugins. It is also suggested by Automattic/WooCommerce to check for the class in their docs.

References:
https://developer.www.ads-software.com/reference/functions/is_plugin_active/#description
https://woocommerce.com/document/query-whether-woocommerce-is-activated/