Postive S-Parameters in a CST Simulation

Hi everyone.
So I'm designing a coupled line microstrip filter for a very first time. I synthesized and tuned a filter in ADS and then tried to export the layout as a DXF file into CST. Following picture is a 3D view of my filter.

Then I tried to run a time domain simulation to verify the design the design. Background material was set to normal and box size seems ok, but the scattering parameters turns out all positive as it's sketched below:

I changed boundary condition and background material in every way possible but nothing changed.
Please help me I'm stuck here for a while.

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