# Discount codes: NULL error message when applying discount

 If you receive an error message that says *NULL* when attempting to apply a discount code, it means that another plugin, script, or configuration on your site is blocking Easy Digital Download's ability to talk to WordPress through the admin-ajax.php.

 This is typically a side effect of using a plugin on the site that blocks access to the /wp-admin/ area of WordPress. To resolve the *NULL* error, start by deactivating all other plugins on your site and then test applying a discount code. If that resolves it, reactivate the plugins one at a time until the problem comes back. Once it has returned, you will know which plugin is causing it.

 If you need to remove access to the /wp-admin/ area, we recommend using the [Remove Dashboard Access](https://wordpress.org/plugins/remove-dashboard-access-for-non-admins/) plugin.