How to check if the Elasticsearch engine is available?
To check if Elasticsearch is running, please execute the following command in the terminal: curl localhost:9200
Note: replace the localhost:9200 with Elasticsearch domain and port accordingly.
After that, you should receive an output containing information about your instance of Elasticsearch. If there is no output, but the Elasticsearch is installed, you may need to restart your Elasticsearch or contact your hosting provider to check the issue.
How Elasticsearch works in Magento 2 →
Elasticsearch Engine Installation Service →
Check out more Q&A about Magento 2 Elasticsearch settings →
See more details on Elastic Search for Magento 2 page