I have downloaded Refined but when I go to Jira Administration > Add-ons/Apps to enable the plugin/add-on/app, it fails and remains disabled.
Reason for this happening
When JIRA starts up, its resources are started too. In rare cases, the resources start in an order that makes Refined believe they have not started, and as it is dependent on the resources, it can't enable.
In most cases this will fix it, and Refined will be enabled. If this does not fix it, please contact us at support.refined.com or support(at)refined.com.