I'm afraid I can't replicate that, the Randomizer works as intended after saving, quitting and then loading. It works so well in fact, it even randomized the debug add pokemon function...
Are the files in the same folder as Game.exe? If not, Here is a Zip file containing the DLLs. Directly from Essentials v19.1. https://ufile.io/5tmjcl48 Paste the DLLs to the Game folder. If doesn't work on the files are already there, maybe you stored the game in a folder that requires Admin...
Just paste the whole zip in your project, or copy contents from The zip's graphics folder to your gane graphics folder, Audio in Audio and Plugins in Plugins.