SW_HIDE doesn't hide my second application C++

Question

I'm trying to open an .exe file with ShellExecuteA() and then hide it. I managed to open the file, but SW_HIDE doesn't work on it, but when I try to do the same thing with notepad.exe, it works.

ShellExecuteA(0, "open", "myapp.exe", 0, 0, SW_HIDE);

This opens my application, but doesn't hide it.

I tried putting myapp.exe in System32, same as where notepad.exe is located so I don't need to use any path beside the app name and .exe extension, but that also didn't work.