Objects Intersect/Non manifold edges in HFSS

Hi Guys,
I am getting a non manifold edges error in HFSS when I unite objects in my design.
If I dont unite them I get objects are intersecting error
The problem is I cannot change the design as it has been imported from CST.
Is there any way around to this?

Whenever this has happened to me in the past, I've had to recreate my setup from scratch.

Sorry and Good Luck!