SendInput doesn't work after the Chorme preview window show

I use C++ program to interact with my web, it will simulate the keys pressing when print page show . key pressing event is CTRL + SHIFT + P .

Using SendInput send pressing event (ctrl + shift + p) for my web page(in Chorme) , function is ok for web page, I have tested it, but it is invalid when the print page show .

why print page show and the SendInput is invalid ? Is print page forbidden key message for ?

 int main() {
  HWND parentHwnd, childHwnd;
  parentHwnd = FindWindow(NULL,"XiaoYouCha - Google Chrome");
  if (parentHwnd)
  {
    childHwnd = FindWindowEx(parentHwnd, NULL, NULL, NULL);
    SetForegroundWindow(parentHwnd);

    Sleep(1000);
    ShowPrint();
  }
}

void ShowPrint()
{

INPUT inputs[6] = {};
ZeroMemory(inputs, sizeof(inputs));

inputs[0].type = INPUT_KEYBOARD;
inputs[0].ki.wVk = VK_LCONTROL;
inputs[0].ki.wScan = MapVirtualKeyEx(VK_LCONTROL, 0, (HKL)0xf0010413);

inputs[1].type = INPUT_KEYBOARD;
inputs[1].ki.wVk = VK_LSHIFT;
inputs[1].ki.wScan = MapVirtualKeyEx(VK_LSHIFT, 0, (HKL)0xf0010413);

inputs[2].type = INPUT_KEYBOARD;
inputs[2].ki.wVk = 'P';
inputs[2].ki.wScan = MapVirtualKeyEx('P', 0, (HKL)0xf0010413);

inputs[3].type = INPUT_KEYBOARD;
inputs[3].ki.wVk = 'P';
inputs[3].ki.dwFlags = KEYEVENTF_KEYUP;

inputs[4].type = INPUT_KEYBOARD;
inputs[4].ki.wVk = VK_LSHIFT;
inputs[4].ki.dwFlags = KEYEVENTF_KEYUP;

inputs[5].type = INPUT_KEYBOARD;
inputs[5].ki.wVk = VK_LCONTROL;
inputs[5].ki.dwFlags = KEYEVENTF_KEYUP;

UINT uSent = SendInput(ARRAYSIZE(inputs), inputs, sizeof(INPUT));
if (uSent != ARRAYSIZE(inputs))
{
    printf("SendInput failed: 0x%x\n", HRESULT_FROM_WIN32(GetLastError()));
} 
}