How to enable maintenance mode
In order to enable Maintenance mode on your website you need first to create a template which to be used and then attach the template when you enable the maintenance mode.
Go to WordPress admin panel. On dashboard sidebar navigate to Templates > Add new.
Select Page type of template > Name your template (optional) > Click on Create Template button. Create your desired template and publish it.
Go back to WordPress admin panel. On dashboard sidebar navigate to Elementor > Tools.
Select Maintenance Mode tab. From the Choose Mode dropdown you can select which mode to be enabled. You can also select who can access your website while it is in maintenance mode. And at the end choose the template you created earlier.
Do not forget to save the changes.