When you spin up a new WordPress site on Nginx, we automatically install Nginx Helper, and the GridPane Redis Object Caching plugin. When you migrate a site in, these may be removed depending on the migration method.
To reinstall Nginx Helper, you can find this in the WordPress Repository and reinstall it from there within your website (inside your site, Plugins > Add New, search for Nginx Helper, click install and activate).
To reinstall the GridPane Redis Object Caching plugin, head over to your Sites page inside your GridPane account and open the website customizer:
Click through to the Caching tab, and then click through to Object Caching. Here you simply need toggle it off and then toggle it back on again. This will reinstall the plugin for you.