Not able to simulate correctly SIW resonator in HFSS-Need Help!

Hi,

I am trying to simulate a SIW based resonator in HFSS,as shown in the figure

I am trying to get the same results as published in this IEEE paper.I have
made this geometry in HFSS and want to plot s-parameters for this structure.

Though HFSS shows no error,but I am not getting results even close to the expected
one, i.e structure should exhibit resonance around 12.46 GHz,

Members,kindly help in figuring out the problem in this HFSS simulation.
I am attaching HFSS 9.2 file for your reference.

Thanks