Timing chain?

Hi everyone, I have a nissan micra E 2004 reg only done 42,000 miles.
My engine malfunction light came on and when we conected a diagnostics computer it came up with the camshaft sencor and timing sencor, the camshaft sencor has now been changed and the light went off. now, the light is back on and the car wont start!! so fustrated dont know what is going on some one said it might be down to poor service history or oil in the car, it culd even be the timing chain! If anyone can help i'd be so gratefull