I looked at your files briefly. Your testbench requires a separate SMD library, and 3D preview doesn't work without adding that.
Your
vias in the Momentum stackup don't exist in layout. There is a layer DRILL_TROUGH in layout, but that is
not mapped in the Momentum substrate. So all your pads are
floating (ungrounded).
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Amendment after looking again at your model: I missed that your substrate
does include the DRILL_TROUGH, but the ground paths are ungrounded for another reason: Momentum doesn't know that your EDGE_BOTTOM is your ground. All your EM ports have the reference at GND =
global ground, which is the nearest infinite ground plane, or in your case some abstract ground reference at infinity. So your "ground" polygons are not connected to the port ground reference.
To make your EDGE_BOTTOM act as ground for the EM ports, you need to place explicit ground reference pins, and assign them to the port's minus terminal in the EM port editor.
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Data display: You have several ports on one polygon, and I have some doubts if your math gives the result that you are looking for. For your pad with a total of 3 ports, you get 25 Ohm input impedance, which is 50Ohm || 50 Ohm from the other two ports.
I guess you want to calcuate shunt capacitance? You can use function stoz(S) and stoy(S) in data display to get the Z values (impedance with other ports open) and Y values (admittance with other ports shorted).