I've had similar problems and solved it by replacing the power cable. It appears the power cable head and/or the device power pin have deteriorated over time.
Additionally, the "internal battery" does not work as was expected and I was told the internal battery is really a capicator with less than expected capability. I always keep a phone external battery and cable in the cockpit in case of an aircraft electrical failure. Make sure the external battery has a high voltage output because of the high requirements of the iFly GPS. Higher requirements than an iPad.