wifi issues following windows 8.1 update

OP posted this on 12/8. It is now 12/11. Either he hasn't linked to the internet or he doesn't want to tell us what the real problem is/was.

After the update you may have to reconfigure your wifi network settings on the PC. Look at the network settings on the computer and make sure they are still configured correctly. Control Panel - Network - etc.

Airplane mode OFF ?

Routers don't have drivers and the drivers for Win 8.1 are the same as for Win 8 so if you had a working driver for your wifi adapter, it should still work.

Have you tried deleting the existing wifi connection and then re-adding it? That seems to fix many of these can't connect problems.

OP: you are confusing us. Are you posting about your router or your wifi?
Routers do not a drivers or updates from Win 8.1.
Wifi can be affected by 8.1.
If it is your wifi, have you called your computer company to see if They have an update to the wifi drivers? It isn't a MS issue if your computer company does not issue driver updates when an updated major release comes out. Companies have lots of lead time to test out their drivers before the update is put out.

I have been using Win8.1 and a router for some time. What router are you using that would only be considered a wifi router? How does the router connect to the internet?

A Windows update wouldn't affect the router. Have you gone into Device Manager and see if there is a yellow checkmark for your network wireless adapter? If not, how many driver's are listed for your wireless adapter? If more than one, keep the manufacturer's driver, and delete the Microsoft updated WIN 8.1 wireless driver.

The router.. or the wifi in your computer? Plenty of google hits on your problem.