Boundary not applicable

Hi.,

I am using COMSOL 4.4 for pressure acoustics Simulation. I have Problem in defining the boundaries. I imported the model from CATIA and capped the inlet and outlet for defining the boundaries but when I choose them to define the boundary conditions I see an error boiundary not aplpicable.(Image in attachment).

I read few Topics here explaining the identities and assembly / Union but coulndt help myself finding a solution

Can someone tell me how can I come over this case when I am importing model from CATIA and working??