laptop display goes black when unplugged

As others have mentioned, I would confirm that the computer is still on and operating normally while unplugged by hooking it up to an external monitor and confirming the image is showing there normally, even if the screen is dark on the monitor itself.

Per resources, it seems a common issue is that your screen brightness overall or the brightness of the unplugged mode is likely too dark.

This post from another forum (https://superuser.com/questions/666410/l...) mentions a very similar issue with another Asus laptop and the resolution was to edit the Power Options within Control Panel (Windows Button > Control Panel > Power Options > Change Plan Settings for desired plan > Change Advanced Power Settings > Display > Display Brightness and ensure you are editing the option for unplugged.

If that doesn’t work, there MAY be a driver issue with the display, Asus support for the R554LA appears to be here: (https://www.asus.com/us/supportonly/R554...) but while relatively simple, replacing monitor drivers on your primary computer without a backup or experience may lead to issues with your display, not allowing you to be able to see anything you are doing on it.