There is a lot of help in the knowledgebase about getting JAB installed and working with your Java application. It is not always as simple as flicking a switch in windows settings, there are instances where your Java app requires a different version of JAB or a manual install of JAB into a non-standard location.
The main thing to remember is JAB is an Oracle Java technology outside of the Blue Prism product. I recommend installing and using Java Ferret and Java Monkey (provided by Oracle with JAB 2.0.2) to test your installation of JAB is working with your application - if not you need to investigate how to get JAB working with your app.