The high frequency part of the circuit have to be developed keeping the wiring between components as short as possible. I'm referring to C3, C4, anode of DIODE1 and DIODE3, cathode of DIODE2 and DIODE4. Thus they cannot be simply accomodated on a strip breadboard.
Furthermore I don't understsand the 50 ohm termination connected to C4. It shoud be instead connected to ground.
In a real circuit you have to connect a coaxial cable from generator to C3 (inner conductor) and C4 (shield) and also you should connect a 50 resistor (using short leads) between the input of C3 and C4 in order to match the generator output.
Another thing. You have to plot the voltage across the load, that is across R1, you instead plotted the output of DIODE1 referred to ground, that is wrong. To do this you have to name also the net on the other side of R1 (for instance VoutG) and plot Vout-VoutG vs. time.
I think that, roughly, the circuit should start to rectify at a generator output power of about 15 dBm