no convergence iterative

I am starting using Feko and I have a little problem...
I have designed a hornantenna feeded with a waveguide excitation. I would like to calculate the S-Parameters. When I simulate only the antenna, I don′t have any problem.
Then I drew a dielectric Cuboid in front of the aperture of the antenna, I enabled volume meshing and I put a second waveguide port after this cuboid (I want to knwo how much power is transmitted through the cuboid)
I chose the meshing suggested by Feko.
But when I run Feko, the iterative solver has no convergence after 500 iterations. What could I do? If I force stopping for a residuum of 0.01, will the result be plausible?

Thank you for your help

Gland

Can you upload your models?

this is my model, but without meshing because i made it with FEKO Lite...
But in my labor, I am using FEKO with all its abilities!

The LITE version is quite limited, I assume your mesh size is too coarse (to fit into LITE) and this is causing the convergence problem. What about surface meshing for the dielectric?