LUCENE regexp sintax not working

Hey guys, recently i provisioned a kubernetes cluster of ES, and Kibana with anothers tools, like filebeat, etc. The problem is with Lucene Search sintax on Kibana Search bar, in a testing install, this sintax: "agent.hostname: /app10[3,4,6,7,8]/" works wheel and match agent.hostanames: app103,app104,app106,... etc, but in production not work this sintax, the KQL is disabled on the search bar, and nothing show when i use the querie. Any body can help me with this?

Thanks, in advance.. sorry for my bad english.

You can check in advanced settings to see what is the default language used for the search bar. Also it will depend on the version of kibana, as KQL is a recent-ish addition to Kibana.