Agile Tools & Filters requires Jira Software (Boards & Backlogs).
It can't be enabled under Jira Core or Jira Service desk.
If you're facing any issues related to the installation please try the following:
- If you've installed the plugin manually make sure you're using the correct app version - DC or Server
https://marketplace.atlassian.com/manage/plugins/io.extensi.jira.plugin.agileboardfilter/versions
Uninstall the plugin and reinstall it again - Create a support request