The debug.log is located in the /tmp dir with in your Journyx install.
The default location on Windows is C:\Program Files\Journyx\jwt\tmp
If you have more than one Journyx app server then you will have a location like this on each server.
If you are on Journyx 11.0 or later, the debug.log file is now called journyx.app.log, but it is in the same location.