You need to diagnose the problem, and then contact the dealer you bought the chairs from so he/she can order you a proper replacement part.
As queendvd2 said, there are 3 components that participate in power recline:
1. Switch with the wires
2. Power transformer
First, check whether none of the wires got caught in the reclining mechanism and got cut. Second, unplug the wires from the transformer and plug them back in. If this does not help get the transformer from a working chair and test it on the malfunctioning one. If this fixes the problem you need a replacement transformer. If not, the chances are this is an actuator, but I would suggest plugging the switch from a working chair just to make sure that the switch is not a problem.
Hope this helps...