Minecraft Launcher does not maximise after using fullscreen mode

I used full-screen mode on Minecraft for a while, but then I decided to just maximize it and keep the border, I found out I couldn't maximize it. I don't know why I can't. Please solve this problem for me. I tried restarting my launcher and logging out of minecraft then logging back in. but it doesn't work. So I am thinking off deleting minecraft then, downloading it again.