Are you using Unity Pro 4.6? Unfortunately, Unity 5 exports assetbundles in a way that PoE can't parse, so this editor is only designed to work with 4.6.
Yeah Unity Pro 4.6, the version recommended by the asset editor download page.
Are you getting any error messages in the console?
Oh wait, I just redownloaded the asset editor from the same page, loaded it up via Unity and suddenly it works as intended. Strange...