If your site is using HTTP Authentication (you know, the dialog/prompt that pops up and asks for your username and password), WP Cron will not work. This is because WP Cron does not present the proper login credentials when making the request. To help with this, there is a free plugin that enables WP Cron when HTTP auth is enabled. Check it out at the WP Plugin Directory: “WP Cron HTTP Auth”.
Hope this will solve the problem.