OrderService is always NULL in production but not in Dev. environment

so result is not null, orderService is not null, but order is?  can you verify that order 3255 exists through yoursite.com/Admin/Order/Edit/3255 ?

or directly with SQL?

result.OrderNumber = 2751 which is the number of the order in NopCommerce. I get this from the order API in mollie. That is the first part the retrieveOrderTask.

Then we get to

IOrderService orderService = EngineContext.Current.Resolve<IOrderService>();

This is the one that is NULL

Full code:

[HttpPost]
        public IActionResult MollieWebHook(string id)
        {
            _logger.Information(id);

            Task<OrderResponse> retrieveOrderTask = Task.Run(() => (_mollieOrderClient.GetOrderAsync(id)));
            retrieveOrderTask.Wait();
            OrderResponse result = retrieveOrderTask.Result;

            _logger.Information(result.OrderNumber);

            IOrderService orderService = EngineContext.Current.Resolve<IOrderService>();

            _logger.Information("OrderService " + orderService.ToString());

            if (orderService == null)
                _logger.Warning("orderService object is null");

            Order order = orderService.GetOrderById(Convert.ToInt32(result.OrderNumber));

            if (order == null)
                _logger.Warning("Order object is null");

            order.PaymentStatus = MolliePaymentStatusToNopCommercePaymentStatus(result.Status);

            return Ok(200);
        }

Also the order does exist. I can see it in the backend also in DB (sql). That is not the problem. And As I said localhost works fine. So like you said it must be the async method. But I dont know.

odd, I don't know why EngineContext would not work.  Does it resolve if you temporarily comment out the async method and retrieve the order with a hard-coded Id?

[HttpPost]
        public IActionResult MollieWebHook(string id)
        {
            _logger.Information(id);

            //Task<OrderResponse> retrieveOrderTask = Task.Run(() => (_mollieOrderClient.GetOrderAsync(id)));
            //retrieveOrderTask.Wait();
            //OrderResponse result = retrieveOrderTask.Result;

            //_logger.Information(result.OrderNumber);

            IOrderService orderService = EngineContext.Current.Resolve<IOrderService>();

            _logger.Information("OrderService " + orderService.ToString());

            if (orderService == null)
                _logger.Warning("orderService object is null");

            Order order = orderService.GetOrderById(2751));

            if (order == null)
                _logger.Warning("Order object is null");

            order.PaymentStatus = MolliePaymentStatusToNopCommercePaymentStatus(result.Status);

            return Ok(200);
        }

Hardcoded test wouldt work. This method is being called by mollie after order placement. As a webhook. Anyways localhost object is perfectly set. Also when I produce an error before IOrderService i get a diferrent stacktrace. After not.

It certainly is odd. Could it be because this class derivese from BasePaymentController?

can you use their testmode?
https://docs.mollie.com/guides/testing

Outside of that, try my previous suggestion of converting the synchronous parts of the method (everything after the async call to Mollie) into a 2nd task, then await them both:
https://stackoverflow.com/questions/55647455/why-is-dispose-called-before-its-finishes-async-task

Alright once again thanks for the quick answer.

Like you said. I tried Task chaining. Wrapped the retrieve order in a Task and the GetOrder in a seperate task. Still the same result. Localhost working. Production version null ref. error. sadly.

New Method with Task Chaining:

[HttpPost]
        public IActionResult MollieWebHook(string id)
        {
            var retrieveOrderTask = RetrieveOrder(id);
            var GetOrderTask = retrieveOrderTask.ContinueWith(t => GetOrder(retrieveOrderTask));

            var rot = retrieveOrderTask.Result;
            var got = GetOrderTask.Result;

            if (rot == null || got == null)
                return NotFound(404);

            return Ok(200);
        }

        private Task<OrderResponse> RetrieveOrder(string id)
        {
            return _mollieOrderClient.GetOrderAsync(id);
        }

        private Task<Order> GetOrder(Task<OrderResponse> response)
        {
            return Task.Run(() =>
            {
                IOrderService orderService = EngineContext.Current.Resolve<IOrderService>();
                Order order = orderService.GetOrderById(Convert.ToInt32(response.Result.OrderNumber));
                order.PaymentStatus = MolliePaymentStatusToNopCommercePaymentStatus(response.Result.Status);

                return order;
            });
        }

object debug on local machine:

rot = {Mollie.Api.Models.Order.OrderResponse}
got = Id = 3371, Status = RanToCompletion, Method = "{null}", Result =
"Nop.Core.Domain.Orders.Order"

Tried the last part with live version.

I dont get any errors and Mollie says the plugin got called successfully in 0.2 - 0.4 seconds.
But the payment status is still unpayed. Wich means nothing changed. Only the method returns a 200 success code.

At last I went with Ydna his advice. I set the orderNumber in the callback url, so now I can properly set the orderStatus using OrderService and it works fine.

Not Ideal since I'm not able to verify the order with the mollie orderStatus.

[HttpPost]
        public virtual IActionResult MollieWebhook(int? orderId, string id)
        {
            if (!orderId.HasValue)
                return BadRequest(400);

            IOrderService orderService = EngineContext.Current.Resolve<IOrderService>();
            Order order = orderService.GetOrderById(orderId.Value);
            order.PaymentStatus = Core.Domain.Payments.PaymentStatus.Paid;

            return Ok(200);
        }

Bizarre, glad you got it working though.