reprap prusa hephestos - extruder stepper motor issue

Hey there, apologies for what is probably a simple question.

I have recently built my prusa I3 Hephestos and am struggling with getting the stepper motor on the extruder to function.
I have checked that it is wired up correctly (the colours were wrong in the kit but they go to the right place so little matter)

If i try to manually jog the motor it doesnt respond at all, but if i try to load filament it pulses.

I've checked that the motor itself is functional by plugging it into another axis and manually jogging it and the motor works perfectly.

Would anyone have an advice on where to start? I am useless a most things electrical

maybe it's the driver which doestn't work... but I can't help further....

Have you heated your hotend?
There is a setting in marlin that prevent a cold extrusion.

//this prevents dangerous Extruder moves, i.e. if the temperature is under the limit
//can be software-disabled for whatever purposes by
#define PREVENT_DANGEROUS_EXTRUDE
//if PREVENT_DANGEROUS_EXTRUDE is on, you can still disable (uncomment) very long bits of extrusion separately.
#define PREVENT_LENGTHY_EXTRUDE

#define EXTRUDE_MINTEMP 170
#define EXTRUDE_MAXLENGTH (X_MAX_LENGTH+Y_MAX_LENGTH) //prevent extrusion of very large distances.