"The app won't run" is too little info.
How are you trying to run it?
Which command are you using to run it?
Is it a Non-ui app?
Any errors on command screen?
If it is an "empty simple b4J app", what do you expect it to do?
Does it at least have a form to show? Or some on-screen logs to show?
Also, running it from the desktop I don't think it automatically grants administration rights to the execution command.
You should try to run from command line making sure to "sudo" your command