Navigation Screen Problem, Is it software? Options

[bobdoe123]

I just bought a 2005 GX470 and the only main problem it had was that it was missing its navigation system (supposedly it was stolen). So I ask the dealer to buy a replacement and install it for me and so they did. Now here comes the problem, nothing shows up in the screen, it just black. However the screen does work when I put the car in reverse and camera turns on. And when I turn on the A/C or the radio on, there a indicator on the screen saying that it been turned on and quickly goes black. Can you please help me?