I ran into this same problem. For me, the problem was I had a dual band router and my laptop was on the 5Ghz wireless network while my LG TV was on the 2.5Ghz wireless network. Once I put them both on the same band, everything worked.
Using ChrisG's method I was able to connect as well (thanks Chris).
My router broadcasts on 5Ghz and 2.4Ghz. With some experimenting I found that the LG TV can connected to the router on 2.4 or 5 or even Ethernet cable, but the PC only works when it is connected to wifi on the 2.4Ghz band. When the computer is connected, on the LG TV go to Settings > Advanced > Network > Wi-Fi Connection and you should see your computer listed with DIRECT-Yourcomputername. So it appears that the PC connects directly to the TV, but only on the 2.4Ghz band.
So the complete solution is:
Connect your PC to your wireless network using the 2.4Ghz band.
Start Screen Share on the LG TV. Under Connection Options, I found normal mode worked better than fast mode.
In Windows 10, press Windows + P to open the projection display settings, then select Connect to a wireless display.
Hopefully it connects. Good luck!
I hope this helps, disappointing that LG support wasn't able to figure this out for people.
Screen Share with Windows 10
in LG TV and LG webOS Smart TV Discussion
Posted
Using ChrisG's method I was able to connect as well (thanks Chris).
My router broadcasts on 5Ghz and 2.4Ghz. With some experimenting I found that the LG TV can connected to the router on 2.4 or 5 or even Ethernet cable, but the PC only works when it is connected to wifi on the 2.4Ghz band. When the computer is connected, on the LG TV go to Settings > Advanced > Network > Wi-Fi Connection and you should see your computer listed with DIRECT-Yourcomputername. So it appears that the PC connects directly to the TV, but only on the 2.4Ghz band.
So the complete solution is:
I hope this helps, disappointing that LG support wasn't able to figure this out for people.