I know this sounds crazy, but try hooking up a close to dead lipo in it. Maybe around 3.7v. See if you can get into it then. I wonder if it's set to a manual lower voltage and anything over that, trips the high voltage protection? I only had this happen one time with a ipo that was charged to 4.24, faulty charger, should have been 4.20. It was a HW also.