PRIORITY!! Very Important to Admins

Hello,
I have found this amazing snippet for an amazing feature that would increase customer loyalty and trust. For a service marketplace, it would be great if the customer can change the order status from processing to complete, by changing the “View” button in his order list to “Approve” when the order status is processing, when he clicks approve, he will be redirected to the order details page in order to confirm his action and approve the order as completed. I have tried this code, it changes the button in the order list from “View” to “Approve” but when the customer is redirected to the order details page, there is no “Approve” button to change order status. Now Please, anyone who knows coding (Unlike me) take a look at this, and find out where the problem is, because if this is fixed, the next step would be to remove “Completed” options from the vendor order details page so he can’t change the status from processing to completed, only the customer can.

// My account > Orders (list): Rename "view" action button text when order needs to be approved
add_filter( 'woocommerce_my_account_my_orders_actions', 'change_my_account_my_orders_view_text_button', 10, 2 );
function change_my_account_my_orders_view_text_button( $actions, $order ) {
    $required_order_status = 'processing'; // Order status that requires to be approved

    if( $order->has_status($required_order_status) ) {
        $actions['view']['name'] = __("Approve", "woocommerce"); // Change button text
    }
    return $actions;
}

// My account > View Order: Add an approval button on the order
add_action( 'woocommerce_order_details_before_order_table', 'approve_order_button_process' );
function approve_order_button_process( $order ){
    // Avoiding displaying buttons on email notification
    if( ! ( is_wc_endpoint_url( 'view-order' ) || is_wc_endpoint_url( 'order-received' ) ) ) return;

    $approved_button_text  = __("Approve this order", "woocommerce");
    $required_order_status = 'processing'; // Order status that requires to be approved
    $approved_order_status = 'completed'; // Approved order status

    // On submit change order status
    if( isset($_POST["approve_order"]) && $_POST["approve_order"] == $approved_button_text
    && $order->has_status( $required_order_status ) ) {
        $order->update_status( $approved_order_status ); // Change order status
    }

    // Display a form with a button for order approval
    if( $order->has_status($required_order_status) ) {
        echo '<form class="cart" method="post" enctype="multipart/form-data" style="margin-top:12px;">
        <input type="submit" class="button" name="approve_order" value="Approve this order" />
        </form>';
    }
}

// My account > View Order: Add a custom notice when order is approved
add_action( 'woocommerce_order_details_before_order_table', 'approved_order_message' );
function approved_order_message( $order ){
    // Avoiding displaying buttons on email notification
    if( ! ( is_wc_endpoint_url( 'view-order' ) || is_wc_endpoint_url( 'order-received' ) ) ) return;

    $approved_order_status = 'completed'; // Approved order status

    if( $order->has_status( $approved_order_status ) ) {
        wc_print_notice(  __("This order is approved", "woocommerce"), 'success' ); // Message
    }
}