I arrive at B12 at ORD not only to no marshaller but to no buildings too.
If you were able to call GSX after landing at KORD (otherwise you wouldn't be able to select the parking in the first place), it means that everything ran correctly so, the only possible reason why you didn't see buildings at KORD, is that you still have the old version, GSX requires to use current 2.0 update, which is a free download.
If, instead, when you landed at KORD that wasn't any GSX menu, that's an entirely different issue.