Materials Studio: Why the "Add" button does not appear in the "Location tab" of the Adsorption locator module?

Dear All,

I am using Materials Studio 8.

While I try to carry out the tutorial "Determining the location of SO2 on the Ni (111) surface with Adsorption Locator" step by step, I faced a problem. The problem:

The "Add" button and "Set maximum adsorption distance checkbox" do not appear in the "Location tab" of the "Adsorption locator calculation" panel? Could you help me to make them appear?

Thanks

MO Fateh