Quadro Sync Module NVAPI Struct Problem in .NET.Reflection

I am implementing the NVAPI GSync Module via Reflection in C#.
I got pretty far and beside 2 functions everything is working fine.
The two functions giving me problems are
NvAPI_GSync_GetTopology and
NvAPI_GSync_SetSyncStateSettings.
Both of them give me an Incompatible_Struct_Version error.

After reading the documentation of the structs and the documentation
of the two functions a felt 1435345634 times I do not know what to do anymore.

The structs I am using look like this:

[StructLayout(LayoutKind.Sequential, Pack = 8)]
public struct NvGsyncGpu
{
public uint version;
public NvPhysicalGpuHandle hPhysicalGpu;
public Nv_Gsync_Gpu_Topology_Connector connector;
public NvPhysicalGpuHandle hProxyPhysicalGpu;
public uint isSynced;
public uint reserved;

    }

   

    [StructLayout(LayoutKind.Sequential, Pack = 8)]
    public struct NvGsyncDisplay
    {
        public uint version;
        public uint displayId;
        public readonly uint isMasterable;
        public uint[] reserved;
        public Nv_Gsync_Display_Sync_State syncState;
    }

The Enumerations used in this structs are defined like this

public enum Nv_Gsync_Gpu_Topology_Connector
{
NVAPI_GSYNC_GPU_TOPOLOGY_CONNECTOR_NONE = 0,
NVAPI_GSYNC_GPU_TOPOLOGY_CONNECTOR_PRIMARY = 1,
NVAPI_GSYNC_GPU_TOPOLOGY_CONNECTOR_SECONDARY = 2,
NVAPI_GSYNC_GPU_TOPOLOGY_CONNECTOR_TERTIARY = 3,
NVAPI_GSYNC_GPU_TOPOLOGY_CONNECTOR_QUARTERNARY = 4

    };

The struct used in this structs is defined like this

[StructLayout(LayoutKind.Sequential)]
public struct NvPhysicalGpuHandle
{
public readonly IntPtr ptr;
}

I calculate the version like this:

public static readonly uint GSYNC_GPU_VER = (uint)Marshal.SizeOf(typeof(NvGsyncGpu)) | 0x10000;
public static readonly uint GSYNC_DISPLAY_VER = (uint)Marshal.SizeOf(typeof(NvGsyncDisplay)) | 0x10000;

And finally call the functions like this:

public NvStatus NvNETAPI_GSync_GetTopology(NvGsyncDeviceHandle gsyncHandle, out uint gsyncGpuCount, out NvGsyncGpu gsyncGpus, out uint gsyncDisplayCount, out NvGsyncDisplay gsyncDisplays)
{
NvStatus status;
uint gGPUCount = 0;
uint gDisplayCount = 0;

        if (NvAPI_GSync_GetTopology != null)
        {
            status = NvAPI_GSync_GetTopology1(gsyncHandle, ref gGPUCount, null,  ref gDisplayCount, null); //this one gives Status=OK

            if (status == NvStatus.OK )
            {
                NvGsyncGpu[] gGpu = new NvGsyncGpu[gGPUCount]; //in test scenario gGPUCount always 1
                gGpu[0].version = GSYNC_GPU_VER;
                

                NvGsyncDisplay[] gDisplay = new NvGsyncDisplay[gDisplayCount];  //in test scenario gDisplayCount always 1                
                gDisplay[0].version = GSYNC_DISPLAY_VER;
               
                status = NvAPI_GSync_GetTopology(gsyncHandle, ref gGPUCount, ref gGpu, ref gDisplayCount, ref gDisplay); //this one gives Incompatible Struct Version

                gsyncDisplayCount = gDisplayCount;
                gsyncGpuCount = gGPUCount;
                gsyncGpus = null;
                gsyncDisplays = null;
            }
            else
            {
                gsyncDisplayCount = gDisplayCount;
                gsyncGpuCount = gGPUCount;
                gsyncGpus = null;
                gsyncDisplays = null;
            }
        }
        else
        {
            gsyncDisplayCount = 0;
            gsyncGpuCount = 0;
            gsyncGpus = null;
            gsyncDisplays = null;
            status = NvStatus.FUNCTION_NOT_FOUND;
           
        }

        return status;
    }

public NvStatus NvNETAPI_GSync_SetSyncStateSettings(uint gsyncDisplayCount, NvGsyncDisplay gsyncDisplays, uint flags)
{
NvStatus status;

        if (NvAPI_GSync_SetSyncStateSettings != null)
        {
            status = NvAPI_GSync_SetSyncStateSettings(gsyncDisplayCount, gsyncDisplays, flags);

            if (status == NvStatus.OK)
            {
                
            }
            else
            {
                
            }
        }
        else
        {
            status = NvStatus.FUNCTION_NOT_FOUND;
           
        }

        return status;
    }

What is wrong with this :-( i do not see where I am messing this up…please give me a hint