Usually when this happens, it would probably means your battery may nee a replacement or there maybe some charger interface plugging in/out problem. Best to get them change or replace a brand new set. Just my 2 cts opiniion
Hi, I had the same issue while device is on and the 'X' sign appear while charging from my Macbook. What I did was, i unplug the cable from the device, and then plug back slowly, and the 'X' sign disappear. Now even though my Tab device is on, I can still charge. You may want to give this a try. Good luck ! Wilson Update: Chances are, your batts are gone. I had the same problem too after using my Tab for 2.5 years, totally cannot charge at all. Replace new batt immediately.