HI alprkrkmz,
I am sorry you are having problems but let me help you.
I would like to verify once again to have a clear picture of your problem. Do you mean that after updating from another Operating System to Windows 8.1 the wireless card is not recognizing the router anymore? Did you do an upgrade on the Operating System or are you referring to a windows update?
As you mentioned, you are using the AC 7260 wireless adapter but do you know what the driver version is?
I would appreciate if you attach your dxdiag report here.
How to get it?
Dxdiag Report: Type dxdiag in Start Menu> open> Save> Copy/Paste here.
Kevin m