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- Manage add-ons: is the JSU app enabled... and all modules enabled (except one, which is disabled per default!)?
- Check your log files, serious problems usually leave a stacktrace. Do you see a reference to a class com.googlecode.jsu.*? (to determent which module cannot be loaded)
- Re-install the app
'Anonymous' User
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Have you tried to remove JSU app and reinstall it in the Jira administration? (Without restarting Jira)
See also https://confluence.atlassian.com/upm/uninstalling-add-ons-273875709.html .
If re-installation of the app in the Jira administration does not work, try to do it with a restart of Jira, follow this steps:
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No configurations (for example workflow or customer field related) will be removed during a re-installation. However, we think it's a good idea to perform a backup before - just in case.