Well, for a few days I was not able to detect my personal WiFi access point running 802.11N at 5GHz, I finally tracked it down to the frequency. I logged into the router and switched it to 2.4GHz and now it shows up in the list of networks and I can connect. How to switch the frequency depends on the router's interface, I use DD-WRT and there is plenty of documentation on it elsewhere.
Maybe the Techs should make a note of this, I get why it would not be advertised (Sorry we don support 5GHz WiFi), but when the issue comes up with a customer asking why he or she cannot detect a WiFi network, a tech should ask, is it running at 5GHz, if so, try switching to 2.4 GHz.
Good day to you,
Edge-Case