Narrowing it down to low fuel pressure and low flow from the tanks and fresh cavitation to the hp fuel pumps and the isa temp at altitude was -20 that day causing other flights on that route to descend to FL250 that day continues to point to super cold fuel causing fuel waxing to not let the engines come up to commanded power. How often do they check the 777 fuel sensor circuit for accuracy once it is installed? Obviously their low fuel temp light didn't come on in cruise but why did the others?