I would like to share my experience and give my five cents regarding this behavior. I have seen many of us struggling with this.
I've built my EVSE v5.5 from scratch. Ordered raw PCB's, parts, etc. 2-3 evenings of soldering work, loaded the firmware and few beers later my new EVSE was ready to test. I've built the EV simulator, connected and the EVSE responded for the commands as it should. Than I connected the cable with a J1772 plug. This cable was a secondhand one, taken from a non functional portable charger. Everything was strait forward, wired it up and connected to my Leaf. And than the surprise: connected, but the charging does not start. What? It was just working fine with the EV simulator, what happened?
Taking it back to the bench I've checked the signaling with my oscilloscope, and here comes the trick. When testing the EVSE using the EV simulator, you always should wire it to the cable end at the J1772 plug! This is important! The cable adds some resistance to the CP circuit and the "Charge" command might result a wrong voltage in the CP line! So in my case to get the 6V "Charge" command I had to adjust the value of R1(620 Ohm) resistor (CP circuit) to a value of 680 Ohm.
I hope this information will be helpful for those who are facing this "issue".