I've had the D3 working for about a year now and today it shut off and now it won't turn back on. I've checked all the connections and everything's fine. The accessory and power lines both have 12 volts and all of the fuses are intact including the one on the back of the D3. The ground wire doesn't have any power running through it. I'm pretty much stumped here and any help is greatly appreciated.

I would still check your fuse.Do a continuity test on your fuses mainly your red acc. wire.The 12v you read may be before the fuse.