Transition between SIW and WR HFSS

the problem is that I can not make the coupling between the slot present in the SIW and WR. I'm not how to set the boundary conditions and what kind of excitement to the structure, particularly for the transition. I tried to create a parallelepid with the size of the slot and then subtract the layer of copper in the SIW. I can see graphically the slot, but the program does not recognize the presence of the transition on the surface.

thank in advance

i hope in your help

uppppp please help

how do I build this structure? such boundary conditions and radiation should be applied to the two structures?

thanks to all