Did you see the documentation if anything is missing out with the slider?
The current version of Celestial Pro is 4.0.2 ,whereas, your site has the far older version of 2.4.1. Hence we recommend you to update the theme and see if it resolves the above mentioned issue.
We can’t assure you the affect upon theme upgrade however you should to take a full backup of your site (files and database) for safety.
You can also export your customizer settings as a backup using this plugin https://wordpress.org/plugins/customizer-export-import/
You’ll receive an update alert inside Appearance>>Themes>>Celestial Reloaded otherwise please check you subscription whether it is valid or not once you login to your account.
[ Enter your license key to Appearance / Theme License menu to activate one-click updates.
When you see a theme update notification you can proceed with the update.]