- they may not be copied properly from plugins/redmine_agile/assets to redmine/public/plugin_assets/redmine_agile/
- the folder plugin_assets doesn't have enough permissions (it should have the same permissions as log, files, and tmp, also there should be the same owner and group)
Otherwise, it can be related to a lack of proper permissions. A certain user (or you) has been allowed only to view the board. The last point to investigate is the correct setup of issue workflow.
To learn more about installing plugins, check our article .