I was given a M6400 and it seems when the power cord is first plugged in the power button LED and both power and battery LED (side LED's) blink blue for a brief second and then nothing. I am unable to power the unit on. The LED on the charging cord is on (blue). 

I wiggle the power cord.. no response.

removed the battery same LED response. replaced Battery with same LED response. 

unplugged and re plugged in power supply. Same response. 

I have had the unit on but unplugged it to move to a different room.