Can't cache this url

http://mysite.com/wp-admin/admin-ajax.php?callback=po_data&orig_request_uri=%2F&action=inc_popup&do=get_data&thefrom=%2Fmoc.ckninuf%2F%2F%3Aptth&thereferrer=&_=1430417130881

Why I can't cache this ?. It's affecting my speed.

I tried everything and in the plugin setting it say this is the best way for cache.