My laptop is Latitude 5285 I think and my problem it shuts down immediately when I remove the charger and I think this is the reason:

So i once opened the motherboard setup (you know the "battery is low" screen, on that screen there are two options to open the setup or the diagnostics I think by pressing volume up or down) 

So I opened the setup and I think I made a mistake and chose "plugged in mode" or something like that 

Since then whenever I remove the charger the laptop force shuts immediately it doesn't even show the "shutting down" screen 

I can't think of any reason to cause this except what I did in the setup 

The laptops battery and charger was working perfectly fine before the accident

Also I tried opening the setup screen later but I never found that "plugged in mode" anywhere please help