You should be able to export GERBER if you have the ADIX license.
Vias are modeled as 3D polygons. If you export GERBER, 3D polygons will be dropped. What I will suggest you to do is to keep a "clean" copy of your structure with layered polygons representing vias. You use the layered polygons model to create your ie3d model for simulation while you can still export the layered polygons to GERBER.