Error while validating the design in CMA

Hello, 

I am trying to simulate a slot antenna in an infinite ground plane through characteristic mode analysis in FeKO. The design contains a slot plus infinite ground and a port feed (voltage source), when I checked the design using CEM validate it shows the following error "Only MoM solution methods are supported in Characteristic modes". The thing I can not understand is although there is an error the simulation is finished and shows results.

Attached is my design.

Any help will be highly appreciated.

Thanks