Hmm… it might be a problem with the normal, a material’s potential name inconsistency or a wrong file directory. --- Post updated --- Is it made to be dependent on the car’s color? If so, that may be what’s causing the problem.
is the parts of the model mapped to the right material? it looks like it can find a material, but is it the right one? did you clear your temp folder and/or 0.29/vehicles folder? sometimes files get written there and end up overwriting any edits. otherwise a look at your code whether just screenshots or so would be nice. we can't help you on the basis of "i did everything right but it doesnt work" because clearly something is wrong