I've designed a Distributed Amplifier in ADS

Hi All,
I've got really confused with this...
I've designed a distributed amplifier with following data using N-MOS (L=0.18um and W=10um) :
fc = 12 GHz , Z0= 50

Then simulate the circuit in ADS , It's cut-off frequency works properly but It's Gain is 0 until 12 GHz!
I've attached two pictures :
1- The schematic of the circuit in ADS
2- The S31 ( means gain, because port 1 is input and port 3 is output)
I've attached the ADS project as well .

Anyone have any experience about distributed amplifier and this problem?

Term1 and Term4 make the SRC Voltage Source short circuit.
Use DC Block..

I used DC Block with Term1 and Term4 As you said but this makes no difference in S31 result. Besides, When I run a DC simulation , nodes have voltage

Kindly upload the project in proper file extension yours is .zap file after i extract the project.zip file.
convert the project folder in zip file and then upload so that one can simulate and see!