Ajax not working for certain user roles

Question

What would cause front end Ajax requests to not work for certain user roles?

I have successfully registered (enqueued) my .js file and I know that I have registered ajaxurl successfully as if I alert(myhandle.ajaxurl) I see the correct path to admin-ajax.php.

When I login as admin, and go to my front end the Ajax executes successfully. However, when logged in with a custom user role, it does not work... In fact, I know it is not executing my PHP file which should be called for the Ajax response as if I enter a error_log entry it does not get written. I know the file is available however as if I add that same error_log entry at the top of the file (outside my function) it does get written!

Is there anything obvious I may have missed?

Here are the snippets of relevant code in use

// My main plugin class

include( MDJM_CLIENTZONE . '/includes/mdjm-dynamic.php' ); // Ajax functions, front & backend

// Class where the enqueue is performed

function __construct()  {
    /* -- Hooks -- */
    add_action( 'wp_enqueue_scripts', array( &$this, 'client_zone_enqueue' ) ); // Styles & Scripts     
}


function client_zone_enqueue()    {
    wp_register_script( 'mdjm-dynamics', WPMDJM_PLUGIN_URL . '/client-zone/includes/js/mdjm-dynamic.js', array( 'jquery' ) );
}

// mdjm-dynamic.php

function update_addon_options() {
    $dj = $_POST['dj'];
    $event_package = $_POST['package'];
    $addons = mdjm_addons_dropdown( array( 
                                        'name'      => 'event_addons',
                                        'dj'        => !empty( $dj ) ? $dj : '',
                                        'package'   => $event_package,
                                        ), false );

    if( !empty( $addons ) ) {
        $result['type'] = 'success';
        $result['addons'] = $addons;
    }
    else    {
        $result['type'] = 'error';
        $result['msg'] = 'No addons available';
    }
    echo json_encode( $result );

    die();
} // update_addon_options
add_action( 'wp_ajax_mdjm_update_addon_options', 'update_addon_options' );
add_action( 'wp_ajax_nopriv_mdjm_update_addon_options', 'update_addon_options' );

// Page where the script should execute

wp_enqueue_script( 'mdjm-dynamics' );
wp_localize_script( 'mdjm-dynamics', 'mdjmaddons', array( 'ajax_url' => admin_url( 'admin-ajax.php' ) ) );

// JS

jQuery(document).ready(function($)  {
    $('#_mdjm_event_package').on('change', '', function()   {

        var package = $("#_mdjm_event_package option:selected").val();
        var dj = $("#event_dj").val();
        var addons = $("#event_addons");
        $.ajax({
            type: "POST",
            dataType: "json",
            url: mdjmaddons.ajax_url,
            data: {
                package : package,
                dj : dj,
                action : "mdjm_update_addon_options"
            },
            beforeSend: function()  {
                $("#event_addons").addClass( "mdjm-updating" );
            },
            success: function(response) {
                if(response.type == "success") {
                    $("#event_addons").removeClass( "mdjm-updating" );
                    addons.empty(); // Remove existing options
                    addons.append(response.addons);
                }
                else    {
                    alert(response.msg);
                    $("#event_addons").removeClass( "mdjm-updating" );
                }
            }
        });
    });
});

P.S. I know I am not checking security I will add this once current issue resolved.

As mentioned, this works in the back end, and also in the front end if logged in as an Admin. Just not when logged in as a user with a custom role. The JS executes as the addClass is working and the mdjm-dynamic.php file is available as I can send msgs to PHP error_log from outside the function when the file is included

Answer 1

OK I found the issue.

When directly entering myurl/wp-admin/admin-ajax.php?action= mdjm_update_addon_options into my browser window whilst logged in as an Administrator, I was getting the expected response of 0. However, when not logged in, or logged in as a non-admin, I noticed I was receiving "You do not have sufficient permissions to access this page".

Looking through my plugin files, I noticed that in my settings class I had the entry...

if( !current_user_can( 'manage_options') )
    die( "You do not have sufficient permissions to access this page." );

Remove this and all is now working fine.