I’ve added a code snippet to the child theme functions.php page to change the “Pay For Order” button on the checkout page to read “Pay Now”. The text hasn’t changed. What am I missing?

    add_filter( 'woocommerce_order_button_text', 'wc_custom_order_button_text' ); 

function wc_custom_order_button_text() {
    return __( 'Pay Now', 'woocommerce' ); 
}