It's weird, the bluetooth and Webcam work perfectly, so I know it's not the cable or card. I think I'm just going to reinstall macOS and see if that fixes it.Presuming that WiFi was working when you got the MBP, it should be easy and free to check the cable connecting the AirPort/Bluetooth to the logic board. This would be more likely a problem if you worked with the slot which the optical drive uses. As noted, WiFi and Bluetooth are on the same board. Is Bluetooth also not working?
Did the diagnostic and it said WiFi is okay, but the icon says "no hardware detected", really odd. I'm going to do a reinstall and update back to this.If bluetooth is working, I'd run diagnostics and see what it says. If diagnostics says WiFi is OK, I would agree and try a reinstall, if it says WiFi is not working, it could be that one of the WiFi chips on the board has gone bad. BTW, I seem to recall that people with bad WiFi boards seem to have issues getting a replacement to work - something to research if you have to go down that route.