Hello. There is a minimum temp threshold that must be reached before the mainboard will let the extruder motor turn. this is usually around 180 but the setting can be changed in marlin. If there is a problem with the temp sensor, that is if your display does not show the extruder temp or if it shows a low temp then you will end up in this same place. If the temp does show the extruder heating up and achieving temp and the extruder motor doesn't turn and you have made no changes to marlin since before it failed then you most likely need a new stepper driver. Your printer should have a GT2560 mainboard with either red A4988 stepper drivers or purple DRV8825 stepper drivers. You can try swapping stepper drivers with an axis like x or y and see if the extruder works and if the axis work. Process of elimination. Report back on the state of your thermistor for E and the results of your stepper driver swapping. FWIW the stepper motor needs to get really hot for the coils to go short and stepper motor failures while they do happen are rare. I have a geeetech i3 pro b myself. It was the first printer I bought. 3 years ago, now. Mine has gone through waves of reworking and has just been a great little machine for years now. Here is what mine currently looks like..