Solution:
Fatal error: Uncaught Error: Class ‘Imagick’ not found
It means that this class is not defined and therefore cannot be found.
Imagick is a native php extension.
You need to make sure that this extension exists on your server and configured. You might need your hosting provider assistance for this or in case you have a full access to the server install it by yourself.
Create a php file with the following code:
phpinfo();
Run it. It should show you all the existing and available extensions on your server. Check that value for Imagick.