Hi there
I can see two issues in the model.
The pipe connected to A1 in the exchanger is just open in the end, as it is just connected to the properties block - connect a reservoir or a chamber to complete the circuit.
The same pipe (port H) is directly connected to a thermal reference. I guess you maybe wanted it to be adiabatic - use a perfect insulator instead.
Try these out, I think it should work.
Good Luck / Juan