Hello!
Unless your laptop had some incident in which the antenna cables were torn (which would be extremely unlikely) the issue is with the wifi card.
Here are the steps to trying to fix your laptop:
1: With the computer off, open the computer and reseat the wifi card. Try disconnecting and reconnecting the antenna cables too.
# If that did not work, try replacing the wifi card.
#
# Here is a useful iFixit manual on replacing the wifi card. It will work for reseating your wifi card as well:
# [guide|61262]
#