xtrons td717?

Hi, I own a 2003 mercedes clk 270. Last week I bought a new xtrons td 717 unit without gps. My problem is, when the old unit was in and I put the key in to the the ignition and turn to the first position the radio started up and when pull out the key goes off. After installing of the new unit this thing is not working. I have power in the unit but is not working with the key. Any idea or experience with this? Thanx