I’m trying to emulate key down and key up in windows. However the behaviour is not working as expected.

In main(), when I press ‘a’, the ‘b’ key should be pressed and stay pressed for 3 seconds. however, it seems to just do a press and immediately release. I expect it to press ‘b’ and keep it pressed for 3 seconds, then release the key.

When sending mouse buttons using SendInput it works. But for keyboard inputs it doesnt want to respect the keydown/keyup flags.

For context, I’m writting a program that uses a single mouse+keyboard to work between multiple machines(cross platform). Why not just use Synergy or some other key+mouse sharing programs? Because I want to learn new things.
The linux versions both work, its just the windows keyboard part that doesnt want to work.
I also asked chat GPT, it told me that this was right, then we got into a circuolar argument, so I need some help from real people, lol.

#include <iostream>
#include <Windows.h>

void SimulateKeyboard(unsigned int keycode, bool press){
    #ifdef _WIN32
        
        INPUT input = {0};
        input.type = INPUT_KEYBOARD;
        input.ki.wVk = keycode;
        input.ki.dwFlags = press ? 0 : KEYEVENTF_KEYUP; // Key down
        SendInput(1, &input, sizeof(INPUT));        
    
    #elif __linux__
        //It works right in linux
        XTestFakeKeyEvent(xConn.display, osKeyCode, press ? True : False, 0);
        XFlush(xConn.display);
    #endif
}

void SimulateMouse(int button, bool press){
    // 0 = left, 1 = right, 2 = middle
    #ifdef _WIN32
        DWORD buttonFlag = press ? 
                            (button == 0) ? MOUSEEVENTF_LEFTDOWN : 
                            (button == 1) ? MOUSEEVENTF_RIGHTDOWN : 
                            MOUSEEVENTF_MIDDLEDOWN 
                            :
                            (button == 0) ? MOUSEEVENTF_LEFTUP : 
                            (button == 1) ? MOUSEEVENTF_RIGHTUP : 
                            MOUSEEVENTF_MIDDLEUP; 

        INPUT input = {0};
        input.type = INPUT_MOUSE;
        input.mi.dwFlags = buttonFlag;
        SendInput(1, &input, sizeof(INPUT));

    #elif __linux__
        //1 left, 2 mid, 3 right for xdotool
        //Hacky and probably unsafe solution, will fix later, but works for now
        if(button==0) system(press?"xdotool mousedown 1":"xdotool mouseup 1");
        if(button==1) system(press?"xdotool mousedown 3":"xdotool mouseup 3");
        if(button==2) system(press?"xdotool mousedown 2":"xdotool mouseup 2");
    #endif
}

void main(){
    while(1){
        if(GetAsyncKeyState('A')&0x8000){
            //This works as expected using SendInput; presses LMB and keeps it pressed for 3000 ms then releases LMB
            //SimulateMouse(0, true);
            //Sleep(3000);
            //SimulateMouse(0, false);
            
            //This does NOT work as expected using SendInput; this presses B and releases it imediatly producing a key press. It should be holding down for 3 seconds then releasing
            SimulateKeyboard('B', true);
            Sleep(3000);
            SimulateKeyboard('B', false);
        }
    }
    return;
}