There are many reasons for this problem; one of the reasons is that Windows Update failed to install or update the Network drivers, in that case, you have to update the required driver manually.

Resetting network settings reinstalls all adapters, erases saved Wi-Fi networks, and custom DNS settings. To perform a network reset, head into Settings > Network & Internet > Advanced Network ...

The year is drawing to a close, so there’s a very good chance that you now find yourself staring straight down the gaping maw of Windows 8. Maybe someone gave you a new Windows tablet or PC as a gift.