JIRA Agile Installation Fails - Unable to load interface class
JIRA Agile is not working and under Administration -> System -> Plugins you may see the following error:
There was a problem loading the module descriptor: GreenHopper License Store.<br/>Unable to load interface class: com.pyxis.greenhopper.jira.license.GreenHopperLicenseStore
Or the following error in the logs:
[atlassian.plugin.manager.DefaultPluginManager] There was an error loading the descriptor 'GreenHopper License Store' of plugin 'com.pyxis.greenhopper.jira'. Disabling. com.atlassian.plugin.PluginException: Unable to load interface class: com.pyxis.greenhopper.jira.license.GreenHopperLicenseStore
When installing the JIRA Agile Plugin there is no need to unarchive the .jar file - if you do so it can cause numerous errors in both the logs as well as in JIRA under Administration -> System -> Plugins. It will also prevent JIRA Agile from functioning correctly.
Simply removing the contents of the unarchived .jar, installing only the JIRA Agile.jar and restarting JIRA will resolve this issue.