You will need to whitelist 2 things:
#1. Use the solution in this forum topic to whitelist wget in the User Agent string > https://forum.ait-pro.com/forums/topic/cron-is-being-blocked/#post-40845
#2. Manually whitelist this valvepress-rankie cron plugin file in the Plugin Firewall Whitelist Tools text box using this whitelist rule: /valvepress-rankie/r-cron.php
When manually creating plugin script whitelist rules, each plugin script/file path that you add MUST be separated by a comma and a space. Example: /plugin-folder-name/example-file-name.js, /example-plugin-folder-name/api/paypal-ipn-script.php, /another-example-plugin-folder-name/example-script-name.php. The path name starts with the plugin folder name (do not add /wp-content in the path name). After manually adding your script/file name path to the Plugins Script|File Whitelist Text Area click the Save Whitelist Options button and click the Activate button.