This plugin relies on the Algolia service which requires you to create an account here. Algolia offers its Search as a Service provider on a incremental payment program, including a free Hacker Plan which includes 10,000 records & 100,000 operations per month. Beyond that, plans start at $49/month.
Algolia Search plugin for WordPress has a few system requirements to be able to work properly.
You will need to make sure your server meets the following requirements:
- WordPress 4.4+
- PHP 5.6 or greater
- MySQL 5.6 or greater
- cURL PHP extension
- mbstring PHP extension
- OpenSSL greater than 1.0.1
Please follow installation steps here: https://wordpress.org/plugins/search-by-algolia-instant-relevant-results/installation/