Unable to search users in admin portal

Issue

Re-indexing has been ongoing for quite some time, and certain users are not being searched in the admin portal or control panel section.

If the above issue arises in a cluster DXP node with an Elasticseach server, execute the following procedures. Please keep the Elasticsearch configuration identical across all nodes in the cluster setup.
Review elastic search logs and check for the shard failure
- The cluster health by running the below command and check that if the server is returning yellow status :curl -X GET "localhost:9200/_cluster/health"
Steps should be followed only during non-business hours
1. Stop all the Liferay nodes
2. Stop the Elasticsearch node
3. Start the Elasticsearch node
4. Start the Liferay nodes one by one
Check the backgroundTaskId and lockId following this documentation and delete accordingly - Stuck-reindex-How-to-check-the-progress-of-a-reindex-process-and-remove-blocked-BackgroundTask-and-Lock-records
Now, if the concern is only with the user, try executing the re-index only for com.liferay.portal.kernel.model.User. It should resolve this behavior.

This is a general approach that can be used in such situations. However, if additional assistance is required, please submit a support ticket requesting support engineer assistance on this by providing the patch details and actions that have already been tried.