Extruder motor not turning

After taking the extruder off my TAZ6 this morning to replace the gears, I find that the extruder motor isn’t turning. I thought I had broken a wire or something, but I see 2.5ohm on both pairs all the way back to the connector on the controller board, and when I plugged the extruder motor into the X-axis, the motor turned fine (and vice versa, the X-axis motor did not move when plugged into the extruder).

So whatever the problem is, it looks like it’s on the board. Which is mighty coincidental given that I took the extruder off… Is there a history of static electricity damage to the drivers? Is there anything else to troubleshoot? I gather there are no separate fuses to the different drivers.

To use the secondary extruder driver, do I have to reflash with the dual extruder firmware?

Found another post that said the extruder won’t move unless it’s hot. Indeed. Nothing to see here.