✅ error 87 when using sendinput windows api to simulate key inputs

[DllImport("user32.dll", SetLastError = true)]
    private static extern uint SendInput(uint nInputs, INPUT[] pInputs, int cbSize);

    [DllImport("user32.dll")]
    private static extern short VkKeyScan(char ch);

    [StructLayout(LayoutKind.Sequential)]
    private struct KEYBDINPUT
    {
        public ushort wVk;
        public ushort wScan;
        public uint dwFlags;
        public uint time;
        public nint dwExtraInfo;
    }
    
    [StructLayout(LayoutKind.Explicit)]
    private struct InputUnion
    { 
        [FieldOffset(0)] public KEYBDINPUT ki;
    }

    [StructLayout(LayoutKind.Explicit)]
    private struct INPUT
    {
        [FieldOffset(0)] public uint type;  
        [FieldOffset(4)] public InputUnion U;
    }   

    private static void SendKey(ushort vkCode, uint flags)
    {
        var input = new INPUT
        {
            type = 1,
            U = new InputUnion
            {
                ki = new KEYBDINPUT
                {
                    wVk = vkCode,
                    wScan = 0,
                    dwFlags = flags,
                    time = 0,
                    dwExtraInfo = 0
                }   
            }
        };

        uint result = SendInput(1, [input], Marshal.SizeOf<INPUT>());
        if (result == 0)
        {
            int error = Marshal.GetLastWin32Error();
            Console.WriteLine($"error: {error}");
        }
    }