Hi Ere, Thanks for your suggestion. The root cause of the issue was I installed the latest version Elasticsearch, 6.5. This version does not work with Koha 18.11, Based on the wiki, I should use Elasticsearch 5.5.x. So I installed the version 5.5.x. It works now. BR, Chee -- Sent from: http://koha.1045719.n5.nabble.com/Koha-general-f3047918.html