Mk8 Extruder not heating

I've been having issues with my hotend not heating after i set a target temperature in pronterface, it also won't heat if i select the preheat on the LCD, i'm using a Prusa i3 kit from sintron and running marlin.

Originally i thought it may have been an issue with the arduino as i was having issues with it connecting to my pc, so i changed it out with another 2560 i have and flashed it with marlin and that fixed the connectivity issues, but i still have the issue with the hotend not heating.

All the other parts work including the HBP heating.

Hi mumblemore i was just wondering if you have solved the problem as myn to is doing the same on my
prusa i3 pro b.. after iv printed a few thing's and have gone to abs from pla my extruder hot end will not heat up so im thinking it's the extruders heater faulty..