Document does not contain both a receptor and a ligand molecule?!

Hi,

I have a pdb-file containing an FAD molecule. I just want to use: Script --> Ligand Interactions -> Show Ligand Interactions with Atoms.

As doing so, DS says: Document does not contain both a receptor and a ligand molecule.

I checked the pdb-file, surely there is the FAD molecule. I tried writing ATOM in the first column or HETATM but it does not work.

What is wrong?

Thank you for your help.