My new KD-55X8505C will only discover a fraction of the WiFi networks that I know are available on my location. And the selection seems to change over time.

Most importantly it the TV is unable to discover the my networks (except for the one I set up with WiFi tethering on my phone). My router and even the WiFi range extender I tried, has never showed up in the list, even though they are in very close proximity to the TV.

Is the TV incompatible with a lot of routers? Do I have to change a setting on the router for it to work? What is going on?