You are wiring this up to what kind of motherboard?
1. Does your computer work properly WITHOUT the uSDC20D installed? You should be able to test this by hooking the computer directly to the car power source without the uSDC20D involved. Using the power on wires to the header on the motherboard touch them together briefly. Your computer should start.
2. Are you sure you have wired the uSDC20D correctly? Double check that all wires from the car to the uSDC20D ARE WHAT YOU THINK they are and that all wires from the uSDC20D to the computer are likewise. Use a digital multimeter to do this.
3. If you are certain you have hooked up the uSDC20D properly, connect the multimeter to the power outputs of the relay. You ought to get zero volts (it's possible you might get a very slight reading, but it would be very low). Turn the car on and check the multimeter. You should get 12 volts if it is working properly.
4. Long shot, but may work. I had a similar problem when hooking up a different type of device that does substantially the same thing as this one does. I reversed the wires that came from the device and went to the power "on" header pins. That fixed it. *If you don't get what I'm talking about, DON'T do it! You could damage your computer if you mistake which wires I'm suggesting that you reverse!*