Running on Linux, I've used launch4j to package an exe.
I copy the exe into my Windows 7 VM, and run it.
And nothing happens.
I run it with --l4j-debug, and nothing still happens (at least, if there's a log file, I cannot find it).
Is there some diagnostic technology that I'm missing here?
Create a console version of your EXE (in the "Header" tab, change "Header type" from "GUI" to "Console") and run that from a CMD prompt.
Most likely you will see an exception message in the console, and that will explain why your app is failing to start.