I stopped at a free EVSE I found on plugshare. When I plugged in the J1772, my Leaf showed the icon for DTC error codes: ( ! ) . I turned the car off/on, then off->ACC->ON, but the DTC persisted. Worse, I could not get the "green car GO" icon when I turned the car On with my foot on the brake pedal.
To get going again, I used the lineman's pliers from the Nissan factory roadside kit to disconnect the negative 12v battery lead for 15 minutes. It was not the "right tool for the job," and it chewed-up the nut a bit, but it worked in a pinch. After reconnecting the 12v battery, the car was happy as a clam: started-up, turned On ("green car go"), and with no DTC error light. I drove to a DCFC, and DC charging worked fine; then I drove home without trouble; then plugged-in at home and L2 charged without trouble (Juicebox EVSE, which I believe does test for a working diode in the L2 charging circuit). I also refastened the battery negative lead with a 10mm socket.
I'm not sure what that DTC was, but it was enough to effectively disable the car. If I'd had my bluetooth ODB2 reader along, I might have been able to clear the code without disconnecting the battery.