1.  Won’t my fuel tank over-float?
Your fuel tank is not supposed to over-float if open after your GEN is shutdown. Over-floating of GEN only occurs
when a part in the carburetor called  float pin is faulty. When this is fixed, the carburetor will no longer over-float when the fuel tank is open with the GEN OFF.
2.     When there is power supply from NEPA, the GEN does not shutdown automatically? 
Check if the the manual override button is in OFF position.
Check if the GEN shutdown wire on the device and GEN is still connected by pressing the GEN shutdown button on the device to OFF the GEN manually.
If the GEN goes OFF after pressing the shutdown button on the device?
It means that the manual override button is in ON position. Press the manual override button OFF.
3.     My GEN did not shutdown with the GEN shutdown button?
Check the wire in the GEN shutdown connector and your GEN if it is still connected.