Passband Substrate Integrated Waveguide filter on CST

Hello

I want to simulate one cavity of a SIW passband filter i'm using CST mws but it doesn't work i have this a message Could not compute matrix factorization

I don't know what is the problem (the structure,exitation,...?)

I tried to simulate one cavity( To see (S11 S21) of a pssband filter without to modeling the cavity again in another progect but i don't find a way,

any one does work on this topic please



i'll appreciate any suggestion
Thank you
Best rgrads