[PaulE]

I have the CTEK version of the Porsche battery maintainer. I'm going to guess that the power socket you have your charger plugged into has a GFI outlet somewhere else on the same circuit and the GFI has tripped. I just verified if I unplug my CTEK from power, but leave it plugged into the cigarette lighter in the car, I can cycle the power button on the CTEK through the motorcycle, car, optima battery and snowflake positions. I actually had the same issue as you a few years ago. I thought the CTEK had died and bought another on Amazon, only to have the same issue. I learned there was a basement outlet with a GFI on the same circuit as my garage outlet and it had tripped. I returned the new maintainer and the original one is still going strong for 17 years now!