trouble registring post type

i use below piece of code to register a new post type in function.php. but the post type won’t register. and when i go to the url domain.com/wp-admin/edit.php?post_type=transaction, the message "Invalid post type" is shown.

add_action( 'init', 'transaction' );
function transaction() {
    $labels = array(
    'name'               => _x( 'Transactions' ),
    'singular_name'      => _x( 'Transaction' ),
    'add_new_item'       => __( 'Add New Transaction' ),
    'edit_item'          => __( 'Edit Transaction' ),
    'new_item'           => __( 'New Transaction' ),
    'all_items'          => __( 'All Transaction' ),
    'view_item'          => __( 'View Transaction' ),
    'search_items'       => __( 'Search Transaction' ),
    'not_found'          => __( 'No Transaction found' ),
    'not_found_in_trash' => __( 'No Transaction found in the Trash' ),
    'menu_name'          => 'Transaction'
    );
    $args = array(
        'labels'        => $labels,
        'public'        => true,
        'has_archive'   => true,
        'supports'      => array( 'title', 'editor', 'author', 'thumbnail', 'custom-fields', 'revisions' ),
        'show_in_rest' => true,
        'show_in_menu' => true,
        'show_ui' => true,
        'show_in_nav_menus' => true,
    );
    register_post_type( 'transaction', $args );
}

i have tried changing menu_position but it didn’t work. activating the debugger won’t show what the problem is either.

p.s. i’m trying to build a theme from scratch; when i use this code in a child theme of any theme (i.e Astra theme) it works just fine!

thanks in advance!