If the WiFi is not working on your Mac due to the "Wi-Fi: No hardware installed" error. Look at the following solution to get it fixed.
Resetting the System Management Controller may help to get rid of this problem
We need to do in different ways on different Macs.
Mac Mini, Pro, or iMac
This case is easy.
1. Turn the Mac off, unplug the power from the wall
2. Wait for a while (about 15 seconds or longer)
Then turn the Mac On to see the result.
New MacBook without a Removable Battery
1. Firstly, Restart the Mac
2. Keep holding the combination of Control + Shift + Option + Power.
3. Release the keys
Finally, Press the Power button to turn the mac back on.
Older MacBook with Removable Battery
1. Turn the Macbook Off completely, Remove the battery
2. Press and keep holding the power button for 10 seconds
Put the battery back in and turn the Mac on. The issue must be fixed right now.