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Have you tried to remove JSU and reinstall it in the Jira administration?
No configurations (for example workflow or customer field related) will be removed during a re-installation. However, it's a good idea to perform a backup before - just in caseYou can remove and re-install JSU without losing any of your JSU configurations. All implemented features stay in your workflows and will be available again after the re-installation.
To remove JSU from your Jira instance:
Log in as a Jira Administrator.
Select the Settings cog, and then select Apps.
In the left sidebar, select Manage apps to view all apps installed on your Jira instance.
Select the JSU app to display the app details.
Select Uninstall. The information summary displays an Uninstalling message and the app will be removed from Jira.