Code 36 is listed in the Operator's Manual as "Engine Stopped Fault - Engine Stopped without Command by Controller"
The first corrective action listed for Code 36 is "Check and fill fuel tank". In other words, it might have run out of fuel.
Despite my suggestion above, I have never actually disconnected the fuel pump wire to run the carburetor empty. I run the generator once a month under load if we aren't traveling and put Sta-Bil in the fuel tank during the winter.