disconnect external keyboard
right click on an empty space, click properties. click Device Manager to the top right, look for keyboard. if you see a keyboard and it doesn't work, then it broke.
if there's nothing under the keyboard category, then there're two possibilities:
1. it broke.
2. the connection became lose.
you might not want to open the laptop and check for the plug, but a lose connection is always a possibility.
or maybe there's a software fix, maybe it's a common problem for your model of laptop, do some research.