I would like to know what could possibly keep my car from starting.

What is your question?

Ok so I own a 2003 Mercedes Benz C240 and the car was running just fine. But one day I came home and went to leave again. About a half hour later The car would not start. Nothing at all. When you turn. The ignition to start it makes a click sound. But it don't turn over to start up I do see all the dash lights come on but as far as starting. Theirs nothing at all. I've changed the starter. And the battery. And had a mechanic looking at it. But he says when his computer is hooked up to it, he still does not read no codes. I'm not sure what the dude even means really. As of why cuz he just does not speak very good English. But I feel like it should not be this hard for someone to know where I'm coming from. Any ideas would help thank you.