Problem in simulating dual band cavity back SIW waveguide antenna

I am trying to design a dual band cavity antenna based on substrate integrated waveguide technology. I have designed the antenna using hfss and when I try to simulate it I get the error that "non manifold edges found for 3 objects". Please help me to solve this problem by eliminating the said error. Prompt help will be appreciated. I hereby also attach the .hfss file of my design and the paper that I am following.