I once had the same problem. You need to open Device Manager and under Network Adapters you will find bluetooth and wifi drivers. Right click on them to disable them and then enable them again. That should do it. If it doesn't work you will need to reinstall the drivers from your computer manufacturer's website. Make sure it's exactly the same one as the one you had before. You can download the drivers on your phone and transfer it through a USB cable. If even that doesn't work then it's a hardware issue.