Unable to insert to PostgreSQL table from ASP.NET MVC project

So I have this small car shop project for university and when I want to place order I get this:

Microsoft.EntityFrameworkCore.DbUpdateException: 'An error occurred while updating the entries. See the inner exception for details.'

PostgresException: 23503: insert or update on table "OrderDetail" violates foreign key constraint "FK_OrderDetail_Order_orderId"

I use .NET Core 3.0.1 and PostgreSQL 4.1.2. The database is deployed on heroku.

The piece of code that causes the trouble:

namespace Shop.Data.Repository
{
    public class OrdersRepository : IAllOrders
    {
        private readonly AppDBContent appDBContent;

        private readonly ShopCart shopCart;

        public OrdersRepository(AppDBContent appDBContent, ShopCart shopCart)
        {
            this.appDBContent = appDBContent;
            this.shopCart = shopCart;
        }

        public void createOrder(Order order)
        {
            order.orderTime = DateTime.Now;
            appDBContent.Order.Add(order);

            var items = shopCart.listShopItems;

            var orderDetail = new OrderDetail();

            orderDetail.orderId = order.id;

            foreach (var car in items)
            {
                orderDetail.carId = car.car.id;
                orderDetail.price = car.car.price;
            }
            appDBContent.OrderDetail.Add(orderDetail);
            appDBContent.SaveChanges();
        }
    }
}

OrderDetail Model:

namespace Shop.Data.Models
{
    public class OrderDetail
    {
        public int id { get; set; }

        public int orderId { get; set; }

        public int carId { get; set; }

        public int price { get; set; }

        public virtual Car car { get; set; }

        public virtual Order order { get; set; }
    }
}

Order Model:

namespace Shop.Data.Models
{
    public class Order
    {
        [BindNever]
        public int id { get; set; }

        
        public string name { get; set; }

        
        public string surname { get; set; }

        
        public string address { get; set; }

        
        public string phone { get; set; }

        
        public string email { get; set; }

        
        public DateTime orderTime { get; set; }

        public List<OrderDetail> orderDetails { get; set; }
    }
}

OrderController:

namespace Shop.Controllers
{
    public class OrderController : Controller
    {
        private readonly IAllOrders allOrders;

        private readonly ShopCart shopCart;

        public OrderController(IAllOrders allOrders, ShopCart shopCart)
        {
            this.allOrders = allOrders;
            this.shopCart = shopCart;
        }

        public IActionResult Checkout()
        {
            return View();
        }

        [HttpPost]
        public IActionResult Checkout(Order order)
        {
            shopCart.listShopItems = shopCart.getShopItems();

            if (shopCart.listShopItems.Count == 0)
                ModelState.AddModelError("", "You have no items in your cart!");
            if (ModelState.IsValid)
            {
                allOrders.createOrder(order);
                return RedirectToAction("Complete");
            }
            return View(order);
        }

        public IActionResult Complete()
        {
            ViewBag.Message = "Your order was processed successfully";
            return View();
        }
    }
}

I've been trying to fix it for a couple of days but still can't figure out what's the problem, that'd be great if some of you guys could help me :)