It could be a multitude of things. You may have to do some troubleshooting to figure it out. First make sure all wires are connected to the metallic switch, if they are, you may have a bad switch. My dad had a Ranger that had a problem where the driver's side switch would lock/unlock both doors, but the passanger side switch would only lock the passanger side door, it wouldn't unlock. He replaced the passanger side switch and it fixed the problem.
It's hard to figure out how to fix your's as I don't know what has been changed to accomidate the new switch.
You may need a multi-meter and some basic circuitry skills to troubleshoot it. Otherwise your only other option is to repair it back to stock and eliminate all other variables with the metallic switch.