The autopilot warning will possibly just be the final act of the basic function disengaging due perhaps to loss of electrical power to it, not to be confused with any drop-out of upper mode functions (selected options) such as alt/AS/hdg hold etc.
Annoying that the media are reporting this as a fuel problem, and double engine failure. The report quite clearly states that the fuel system as tested was fully functional, the engines did NOT fail, they simply stopped due to lack of fuel. There was fuel available, just that for whatever reason the pilot had de-selected the only method of getting it to the engine supply tanks.