HFSS error in microstrip line simulation: Port refinement, process abcd3 died

Hi,
I am using HFSS version 9 and I am new to HFSS. I am in the process of simulating a microstrip line. I am getting this error saying "Port refinement, process abcd3 died unexpectedly" This happens when I increse my modes in port 2 up to 5. It works until 4 modes. Can an expert explain me regarding this?

Thanks!!

I'm not sure. Are you sure your setup frequency supports 5 modes? If not, increase the setup frequency.

Hi,
Thanks for the reply. I chenged the dimensions of the ports. Now I can go up to 5 modes. Not sure why it is so.