The UVs are a mess on every channel this is why you cant add anything to the mesh on the glass as it isnt unwrapped propperly in Maya !..
Which version of Maya are you useing i guess it is the LT Student version of maya as my commercial version will not reconize the file but ue4 can pick this up straight away.
re do you UV maps on every channel - and unwrap them proppperly in maya you will get a better result .
Also scale the car up its really tiny its like a hot wheels car scale size this isnt real world scale.