Did the Ebay listing specify which version of the box you bought and/or which version of the firmware was currently installed on the box?
It's possible it's not an Audi variant, so you should apply the Audi version of firmware.
You can do this using my DMS tools, selecting the option 'Reflash box' and unchecking the option 'Install non-hacked firmware'. Once the firmware update is applied by the tools, simply pop on a single playlist of music and go put the DMS in the car.
It'll run through a routine of updating the firmware which can take upwards of 10-15 minutes (lots of flashing green)...but then hopefully things will kick back into life. If not, and you use the latest version of the DMS tools I released over the weekend, then run 'Boot Check' process.
If it tells you you need to put the DMS back in the box, do that, fire it up and give it a couple of minutes (or until it noticably puts lights on and turns them off in an apparent sequence), and run the 'Boot Check' again which will give us an indication if the box is booting successfully or not.