First, check to make sure the battery is charged and in the “on” position. When the battery is charged and on, LEDS on the battery illuminate to indicate the charge status.
Second, check the connection from the battery to power cable, controller and LEDS. It is not uncommon for the power cable to become disconnected from the battery if there is not enough slack in the power cable through the collar loops. If this is the problem, readjust LEDS, controller and power cable to ensure there is slack in the power cable between the collar loops.
Third, after checking battery and connections, turn battery off and on to reset the controller.