Protect cBot with machine ID - Error iphlpapi.dll

Hi developers,

maybe some c# eperts can help me.

I'm trying to protect a cbot based on machine ID (MAC address).

but wenn I use my code I receive the error: "Crashed in OnTick with DllNotFoundException: Unable to load DLL 'iphlpapi.dll' or one of its dependencies: 0x80070005 (E_ACCESSDENIED)".

I checked my windows folder, the 'iphlpapi.dll' is in there. So how could I solve the problem? Any ideas what the reason is and how to solve it?

here is the code I use for checking the machine ID:

using System.Net.NetworkInformation;

...

...

...

  public string getMacAddress()
        {
            String firstMacAddress = NetworkInterface
                .GetAllNetworkInterfaces()
                .Where(nic => nic.OperationalStatus == OperationalStatus.Up && nic.NetworkInterfaceType != NetworkInterfaceType.Loopback)
                .Select(nic => nic.GetPhysicalAddress().ToString())
                .FirstOrDefault();

            return firstMacAddress;
        }

I