How to prepare protein-ligand complex pdb for generating 2-D figure in LigPlot?

previously,I have used i-tasser for ab initio modeling of my protein sequence for its receptor and inhibitor and than I obtained my both pdb models(receptor and inhibitor) and than performed it for protein protein interaction by using patch dock server but after ploting its complex with ligplot its appears a error :-

"No atom coordinate found.possibly this case is too difficult to plot"

so, please suggest me the solution about my problem.