The tasers work by running a current between 2 points. Because the human body is a poor conductor of electricity, the current is diffused through tissue which overloads the nervous system in the muscles and immobilises the victim.
If the 2 points of the taser hit a metal cuirass, apart from the question of penetration (which the tips aren't strong enough to do) to attach to the cuirass, the metal would be an excellant conductor of electricity so the current would pass quickly and directly from the positive to the negative tips. At best, there might be some diffuse current which may be felt where skin touched metal but it would probably be no stronger than a battery on the tongue, or in this case, since we are talking about a cuirass, applying a battery to the nipple (but enough of Nia).
So it shouldn't disable the target.
Unless he was hit where the cuirass was not. Say, under the guiding dorsal feathers....