C++ SendMessage / PostMessage WM_KEYDOWN WM_KEYUP doesn't work

Question

I'm attempting to press the Left arrow key button and Right arrow key button.
The Window Handle I'm passing in is correct. (see screenshot below)

I used Microsoft Spy++ to figure out the correct PostMessage when I press Left/Right keys.

Here are the screenshots showing the lParam and WParam

First 2 screenshots are VK_RIGHT (WM_KEYDOWN & WM_KEYUP)
Next 2 screenshots are VK_LEFT (WM_KEYDOWN & WM_KEYUP)

Here is the code I attempted to use it works by pressing NUMPAD1,2,3 to test out whether or not the VK_LEFT OR VK_RIGHT works.. (none of them work).

gKey(VK_NUMPAD1) //crap testing
        {
            windowHandle = FindWindow(L"SSClientMainWndClass", NULL);
            printf("window handle = %x\n", windowHandle);
            PostMessage(windowHandle, WM_KEYDOWN, VK_RIGHT, 0x414D0001);
            //Sleep(1000);
            PostMessage(windowHandle, WM_KEYUP, VK_RIGHT, 0xC14D0001);
            Sleep(1000);

        }
gKey(VK_NUMPAD2) //crap testing
        {
            windowHandle = FindWindow(L"SSClientMainWndClass", NULL);
            printf("window handle = %x\n", windowHandle);
            PostMessage(windowHandle, WM_KEYDOWN, VK_LEFT, 0x414B0001);
            Sleep(1000);
            PostMessage(windowHandle, WM_KEYUP, VK_LEFT, 0xC14B0001);
            Sleep(1000);
        }

Here are the screenshots of pressing the VK_NUMPAD1 in the game. (The Post message is sent to the correct Window and the information seems correct!)

Answer 1

Maybe you need to run your program as administrator, you can't send input to a process more elevated than yours. I used keybd_event() and it always worked for me, with the mention that Home/End require KEYEVENTF_EXTENDEDKEY.

I know this is old, but I was looking for something similar and saw this has no answer.