My code doesn't work for motor control via the Raspberry?

I'm trying to build a controller for a miniature crane using a Raspberry Pi. The controller runs via an HTML website (according to Chat-gpt, this is the correct one; just ask if you need the script). As soon as I press the button on Putty, I get a message saying that the GPIO pin isn't a pin on the Raspberry Pi.

This is the code:

 using Microsoft.AspNetCore.Mvc; using System.Device.Gpio; using System.Numerics; namespace Kransteuerung_MEKW.Controllers {  [ApiController]  [Route("[controller]")]  public class CraneController : ControllerBase  {    private readonly GpioController _gpioController;    private readonly ILogger<CraneController> _logger;    public CraneController(ILogger<CraneController> logger)    {      _logger = logger;      _gpioController = new GpioController(PinNumberingScheme.Board);      var allOutputPinNumbers = new List<int>{ 3 };      _logger.LogInformation("Setze alle GPIO Pins auf Output start");      foreach (int pinNumber in allOutputPinNumbers)      {        var pin = _gpioController.OpenPin(pinNumber);        pin.SetPinMode(PinMode.Output);        pin.Write(PinValue.Low);      }      _logger.LogInformation("Setze alle GPIO Pins auf Output fertig");           }        [HttpGet()]    public string Info()    {      return "Mögliche Posts: crane/turnLeftStart oder crane/turnLeftStop";    }    [HttpPost("turnLeftStart")]    public void TurnLeftStart()    {      _logger.LogInformation("Kran dreht links start");            var pin = _gpioController.OpenPin(3);      pin.Write(PinValue.High);    }    [HttpPost("turnRightStart")]    public void TurnRightStart()    {      _logger.LogInformation("Kran dreht rechts start");             var pin = _gpioController.OpenPin(4);      pin.Write(PinValue.High);    }    [HttpPost("turnLeftStop")]    public void TurnLeftStop()    {      _logger.LogInformation("Kran dreht links stop");      var pin = _gpioController.OpenPin(3);      pin.Write(PinValue.Low);    }    [HttpPost("turnRightStop")]    public void TurnRightStop()    {      _logger.LogInformation("Kran dreht rechts stop");      var pin = _gpioController.OpenPin(4);      pin.Write(PinValue.Low);    }  } }