Your path is probably not valid, to get the proper path copy it from the editor, by selecting the asset and doing Ctrl+C. It should look something like this :
"StaticMesh'/Game/Props/Cart/CartA.CartA'"
And btw, it’s pretty obvious from your 2 post that you do not understand what you are doing, for example
FVector offset;
offset = FVector(0.0, 0.0, 0.0);
does absolutely nothing. This is really basic stuff, you should do some tutorial on Unreal 4 or C++ programming in general.
Here is a good link : https://www.youtube.com/playlist?list=PLZlv_N0_O1gaCL2XjKluO7N2Pmmw9pvhE