i too am having this issue, i have checked the extruder motor, by swapping it with x-axis, stepper moves and responds to x commands.
swapped the stepper board, also good, also checked to see if there was a miss-wired mosfet, all normal
the printer worked prior to the upgrade to the latest firmware, so i am pretty sure its firmware or settings.
its a rostock mini pro with an ATMEGA 2650, i retrofitted a z-probe and a hot bed.
i have run preheat, and temp went higher than 190, still no luck on e-axis
i have done a ton of tuning and don't want to lose a days work. there seem to be more than a few threads on this type of issue, so i was hoping you might have some insight, i have checked other threads
any help would be appreciated.