Enable debugging in WP into file wp-content/debug.log

wp-config.php

<?php
//  paste directly above: "/* That's all, stop editing! Happy blogging. */"
define('WP_DEBUG', true );
if ( WP_DEBUG ) {
	define( 'SAVEQUERIES',      true );
	define( 'SCRIPT_DEBUG',     true );
	define( 'WP_DEBUG_LOG',     true );
	define( 'WP_DEBUG_DISPLAY', false );
}