Microsoft doesn't build the router or the wifi card or the wifi driver. Go to you ISP, router, PC vendor and wifi cards forum and support and let them know. They are the only ones that can fix it.
Outside of the Surface Microsoft doesn't manufacture the final unit. There are a million things that can cause the network to not work and none of them are Windows 8.1. Sure a setting in 8.1 can get messed up but that isn't the OS or an update they did that would because something else messed it up.
Most of the issues are caused by 3rd party software that Microsoft has no control over. Start your PC in safemode with networking that will give you a clue. Next use clean boot. Is any of those work they it is 100% not windows.
If safe mode doesn't work chances are its your ISP router or network driver that needs to be updated or reinstalled.
This will help
http://www.vindamedia.com/windows/help/troubleshooting-your-network