If you want to study the in-plane electron transport, the C-axis should be parallel to the graphene-MoS2 plane because the C-axis is a transport direction in ATK by default. As far as I can see in the script, this requirement is not met in your setup.
Moreover, the C-axis (transport direction) should be orthogonal to the A and B axes (cross section plane), or in other words the electron transport direction is to be orthogonal to the cross section area of the device assumed in ATK to be given by the AB plane. It means that when you match the graphene and MoS2 sheets in the Interface builder plugin, you should chose a matching in-plane supercell that has a rectangular shape.