How do I properly setup a Characteristic Mode Analysis (CMA) solution of a Patch Antenna (w/Substrate medium included)?

Hello!

I'm trying to solve CMA for a standard rectangular patch antenna. Specifically, I created a dielectric box (assigning the region a permittivity value of 4.4) with dimensions sub_length = 1, sub_width = 1, and sub_height = 1.56e-3, along X, Y, and Z, respectively. Next, I created a second dielectric box with dimensions patch_length = 0.5, patch_width = 0.5, and patch_height = 1.56e-3, along X, Y, and Z, respectively. Then, I clone the second box and subtract it from the first box. Now, I have two non-overlapping box structures, where I assign the top face of the second box a PEC boundary. Finally, I unite the two structures and assign the bottom face a PEC boundary.

I set my operating frequency as 300MHz and selected the characteristic mode solver for 10 modes. Unfortunately, the FEKO solver runs into an issue: 

ERROR 37590: The characteristic modes that were calculated are all non-radiating

Does anyone know how I can solve this problem in this FEKO version?

I am attaching the project file for more info.

Thanks!

Ricardo