Hi,
A reverse plug only affect motor's direction,
so it should work but counterclockwise instead of clockwise.
First, there's a low temperature protection.
The extruder won't run until hotend is warm enough.
If it still does not work, when heated,
the extruder's driver has to be cheked
because drivers are fragile, especialy cheap ones.
Try to invert the extruder's driver with the X one,
and test both X and E axis.
If the extruder's driver don't work on the X slot,
consider it out of order.
If the extruder's driver works on the X slot,
and not the X one on the extruder's slot,
maybe your board have a problem.
Eventualy check for dry solderings
or ask for a fully working component.
++JM