Our company server for JIRA (v 6.2.2) was failed one day. After I reinstall the JIRA and reconnected it to the original database, I found the Agile plug-in is missing. Since our licence of Agile for support was expired two years ago, I manually installed a old Agile add-on with version 6.3.7.
After that, the JIRA gave me message "JIRA Agile is currently unavailable. This might be because an upgrade task has failed to run or has not not yet completed."
Is this a problem with the database or wrong version of the Agile.