Populate a selewct list in a CPT from values set in a Settings Page

Further to this I have this code that shows the select list in my product CPT but the list is empty:

add_filter( 'rwmb_meta_boxes', 'register_custom_meta_boxes' ); // Hook into Meta Box to register custom meta boxes

function register_custom_meta_boxes( $meta_boxes ) {
    // Retrieve stored values from the settings page field
    $options = get_option( 'prod_cats_test', [] ); // Replace with the actual field key inside your settings page

    // Ensure values are correctly formatted before populating the select field
    if ( is_array( $options ) && !empty( $options ) ) {
        $formatted_options = array_combine( $options, $options ); // Convert array into key-value pairs for the select field
    } else {
        $formatted_options = []; // Fallback to an empty array to prevent errors
    }

    // Define the custom meta box for the specific post type
    $meta_boxes[] = [
        'title'      => 'Product Categories', // Title of the meta box
        'id'         => 'custom_select_meta_box', // Unique ID for the meta box
        'post_types' => ['product'], // Specify the post type(s) where this meta box should appear
        'fields'     => [
            [
                'id'      => 'product_cats', // Field ID for storing the selection
                'name'    => 'Select an Option', // Label for the select field
                'type'    => 'select', // Define the field type as a dropdown select box
                'options' => $formatted_options, // Populate dropdown dynamically
            ],
        ],
    ];

    return $meta_boxes; // Return the modified array of meta boxes for registration
}