Netgear sells various "N300" extenders (travel, desktop, wall outlet). The "300" indicates the speed of the extender and the "N" indicates it supports 802.11n, which only covers the 2.4 GHz band.
With an "N" extender, you will need to first go into the ASIAIR Settings window and disable the "5G WIFI" selection. Then execute a "shutdown" from the same ASIAIR window, then reboot the ASIAIR box after the green Raspberry Pi LED has stopped flashing.
See if that will allow your N300 to see the ASIAIR WiFi access point, and finish the configuration.
Good luck.
Chen