Beacons are only configurable for a period of 30 minutes after they are initially powered. After this 30 minutes period elapses, the beacon will no longer be connectable from other Bluetooth 4.0 devices. This feature is a security precaution to limit the possibility of third party manipulation of your beacons once they have been installed and configured.
If you are unable to discover your beacon using the RadBeacon Config App, remove the plastic cover and firmly press the configuration button located above and to the right of the battery holder. This will restart the 30 minute configuration window and your beacon should show up in subsequent scans.
This Article is for the RadBeacon Tag (the battery powered iBeacon), if you are configuring a RadBeacon USB please see this article.