There may be several reasons why the connection was unsuccessful, please check if any of the following reasons may be in conflict:
AirPatrol WiFi supports WPA-PSK and WPA2-PSK security modes.
Only 2.4GHz band is supported (5GHz band is not supported).
AirPatrol WiFi requires a router that is compatible with IEEE 802.11 b/g standards. IEEE 802.11a/n/ac (and other, more exotic) standards are not supported.
AirPatrol WiFi might have connection problems if your installation location has a very weak signal to your router or there is strong interference on 2.4GHz channels. It might be helpful to perform the pairing process in close vicinity to your router and install the WiFi unit on your wall later on, when it already has a working connection to your router and Internet.
Your WiFi router must not be configured to run in 802.11n or 802.11ac-only mode. Usually mixed modes are not a problem but if you have disabled 802.11b/g modes or forced wide (40 MHz) WiFi channels then AirPatrol WiFi will be unable to communicate with your router. To be sure this is not the issue, you might want to try to set your router to 802.11b/g-only (or as it is called in case of some router models - "Legacy" mode). It is likely that if these settings work, they are only needed during the pairing process and you can revert to your preferred settings once pairing has been completed, although 802.11b/g must still be enabled in your router.