If you are having trouble pairing the bulb to your hub, make sure that you initiate the pairing process from the hub within three minutes of powering the bulb on. After being powered on for three minutes, unpaired Element Touch bulbs will exit factory reset / pairing mode and turn off. Simply power the bulb off and on again to re-enter factory reset / pairing mode.
If the bulb has already been successfully paired with a hub, then the bulb may potentially be out of the hub's range. Try moving the hub to a central location in the home, as the distance between the bulb and the hub may affect the connection.
If the bulb is within range and was working fine with the hub, but has now lost connection, try resetting and pairing the bulb again.