This only happened after switching ISP (went from Fios to TWC). TWC tried different methods but all failed. I still had LIMITED connectivity on my wifi. I knew it was something with my laptop because when I connected Ethernet cable it worked. Also, my 5G devices picked up the 5G wifi and that worked. It's the 2.4MHz wifi that was not working with windows 8.1, maybe something to do with dual band routers??? I dont know. I'm not a techie - but I resolved my issue:
SOLUTION: Uninstall and then reinstall your wireless driver..
1) You probably cannot access the internet at this time so connect via ethernet cable.
2) Now lets find the existing driver on your system and delete it. Click on the windows button (4 rectangles), then type my pc
3) Right click on this PC.
4) Go to the Lenovo drive (D: for me)
5) CLick on Drivers
6) CLick on WLAN
7) Double click SETUP and uninstall the existing driver
8) Now lets find your new driver: Go to support.lenovo.com
9) Find your lenovo product (model is underneath the laptop)
10) Select Wireless LAN from the COMPONENT drop down.
11) Select your OPERATING SYSTEM from the other drop down (Windows 8.1, etc)
12) Find ATHEROS WLAN DRIVER and download and save it on your computer
13) Repeat steps 3 to 7 to install the new driver
14) Connect to the internet, but this time without being LIMITED
