I have a Latitude E7240 with AC-7260 and I have a TP LINK router wr741nd. I can't see the WiFi network of this router from my notebook but I can see this WiFi network from my Galaxy S5 and from other notebooks.
I thought It was a problem of the network card but I can see other WiFi networks.
I have Windows 8.1 installed in my Latitude.
Is the name of the network (SSID) hidden? If the router was setup to not broadcast the SSID, the network will not be visible. Try checking the router settings or creating a new connection and adding the SSID and password manually.
Another possibility is that the wireless adapter was set to 802.11a for some reason and therefore, it would only work at 5 GHz. Make sure the wireless mode is 802.11a/b/g.
Based on the description I believe those are the only two possible causes but let me know if you need further assistance.