How Do I Rebuild My Sitemap?

Having severe sitemap issues. For some reason my sitemap is not showing up properly meaning Google n Bing are having issues indexing it.

I have searched for a manual rebuild option but haven’t found anything of the sort on the WPMU dashboard or in the Infinite SEO settings. Could someone please advise?

Is it just that I cannot see the sitemap? The path is http://possesocialmedia.com/sitemap.xml