CST aperture coupled antenna far field computation issue

I am trying to simulate an aperture coupled microstrip antenna in CST microwave studio but it is giving error
"parallel symmetry planes! No farfield calculation possible"
What is the problem I haven't set any symmetry plane! why i am not able to get fafield data.

may be you need to check the boundary conditions and ensure that they are all open

I have encoutered the problem before,

The important key is that discrete port or waveguide port what you use.

Please use waveguide port to solve this aperture coupled antenna model