Sounds like the box is not booting correctly....if you have the version of the DMS tools that has the 'Boot Check' button, use it.
If not, download the latest version of the DMS Tools and then use that button!
Take the DMS out to the car let it have a go at booting, and the bring it back to the cradle, start the DMS tools and click on the button again.
It should then tell you what's wrong and we can help you more from there.