@calbzam We have diagnosed the bug and fixed it with a workaround. After we encountered the same problem with another computer with Windows, we have realized those computers have Turkish language as their Operating System Language. When Plastic creates jira.conf in Turkish OS, it creates it as jıra.conf not jira.conf. Because lower cased I is ı in Turkish, and you are probably creating and reading jira.conf with a lowecase(JIRA.CONF) function. Plastic Client also searches directory as jıra.conf so it never finds our jira.conf file.
We have changed the jira.conf file names to jıra.conf in our Turkish OS installed PC's, and it works now. But you should fix it on your side.