1. Make sure your anti virus does not destroy the extraction, various ones like kaspersky flag it as a false positive.
2. Make sure you are using worldedit version 1.21, not the lattest which 1.24 odd as JNGP does not work on versions newer or older than 1.21. This is the version of your worldeditor.exe file I am talking about, your game can use the lattest patch but inorder to use JNGP you just have to change the worldedit.exe for an old 1.21 one.