Hello @fabiovito83,
Skipping the cache when a cookie is present in the headers is expected behavior and it is how the caching is designed to work. Note that the cookies may store visitor’s sensitive data. The presence of a cookie in the header is instructing the server that there is private information on the page.
Bypassing the cache on such pages is how we are ensuring that this private data would not be served to other visitors. Note that this is not controlled by the SiteGround Optimizer plugin itself, but by the SiteGround Nginx configuration. That being said, there is no option to exclude a cookie within the settings of the plugin and activate the caching while the same cookie is present in the headers.
In regard to woocommerce_recently_viewed, it is a cookie added by a WooCommerce widget. I did some research online, but I could not find a way to disable the cookie except for disabling the Recently Viewed Products. I would advise you to get in touch with the WooCommerce team for additional instructions on how to disable the cookie.
Best Regards,
Kuzman Stoyanov