Sometimes you might experienced an awkward problem of not loading menus or submerses or drop-down menus in WordPress dashboard. It occurs because of JQuery or ajax file not loaded successfully and most of the times it happens after installing a new plugin or updating existing plugins or themes. You can solve this error by two simple tricks. Here is the tips to solve WordPress JQuery dropdown or dashboard menu problem.
Open wp-config.php file from your WordPress root directory and add the following line at the end of the line.
/** To solve Dashboard JQuery drop-down menu error or Ajax problem. */
define( ‘CONCATENATE_SCRIPTS’, false );