Re index of Zephyr for Jira takes long time and some times doesn't even complete in a clustered environment
1.In a clustered or Jira data center environment make sure all the nodes as "active" or up and running and not disabled (You can check this in your Jira Administration page)
2.Even if one single node is disabled Zephyr for Jira can show some abnormality in re index and also while adding test cases to test cycles .
3.Since all the node's data points to a data center there can be difficulties in re indexing even if one node is disabled
The best practice is to make use of your clustered environment or Jira Data center efficiently especially when you have a lot of projects and users accessing the application from different parts of the globe.
With huge automated test cases or imports into projects taking place its recommended to do a re index at least once a week in your off business hours .For all this to be possible all the Jira nodes created should be active