gain of N-port amplifier model simulated in Ansoft EM simulation shows error

Hi,

I am simulating an amplifier in EM mode of Ansoft by importing the S2P file as an N-port model. Using the circuit designer with ideal loads of 50 ohms, I get the right gain (S21 parameter) of 13 dB. When using microstrip lines with physical dimensions corresponding to 50 ohm load, it shows -3 dB gain.

I don't understand what I am doing wrong. Could someone please point out the error?

I have attached the adsn file.

Thank you,amplifier_N-port.zip