On a new installation, make sure that DC power (12 or 24 volts depending on the model) is connected to the red and black wires with correct polarity. When this is confirmed note that the UnLatch will never operate unless the springlatch plunger is pushed in by the springlatch. You can be "fooled" by this feature if you're trying to test operate the UnLatch with the door open. To circumvent this, use a pencil or other similar object to lightly push in the springlatch plunger and then close the trigger wire to +V and you will see the UnLatch plungers move. On a service call for a unit with successful operating history, in addition to the checks mentioned above, check to see if the door and latch have gotten into a warped situation where there is heavy pre-loading on the door. The UnLatch motor may not be able to release the latch under this condition, but you should be able to hear it trying to release the latch. The UnLatch will automatically shut down its motor if it can't release the latch within 1.5 seconds. It will operate normally when it is re-triggered. You should be able to try operation by removing the pre-loading by pushing the door closed with enough force to counteract the pre-loading. Note that this situation is more likely if power supply capacity is less than the recommended 3 Amps at 12VDC 1.5 Amps at 24VDC. To correct this "warped door" situation, have the door serviced and possibly increase the capacity of the power supply.If the unit still will not function, note that it does have an internal microprocessor that could have gotten into a crash condition. This can happen some times if the unit is under-powered and has consequently stalled (the motor is not receiving enough power to operate the latch). While the motor is in the process of stalling, voltage to the processor will sharply drop and this can crash the microprocessor. A crash can also occur as a random event but this is unusual. The recovery technique is to de-power the unit, and then re-power it with the red and orange wires already connected (both then connect to +V). This re-initializes the firmware. Naturally, once this operation has been performed, return the unit to standard wiring (orange only connects to +V to trigger the unit.)Finally, the unit could have experienced motor failure or other internal electronic failure. Call the factory.