Facebook share button not showing until after refresh

It is because sometimes your FB object is not even defined, and your FB.XFBML.parse() function gets called. You need to make calls to FB object when it has initialized. So your code changes to this :

<script>
   (function(d, s, id) {
          var js, fjs = d.getElementsByTagName(s)[0];
          if (d.getElementById(id)) return;
          js = d.createElement(s); js.id = id;
          js.src = "//connect.facebook.net/en_US/sdk.js#xfbml=1&version=v2.0";
          fjs.parentNode.insertBefore(js, fjs);
        }(document, 'script', 'facebook-jssdk'));

     window.fbAsyncInit = function(){  // this gets triggered when FB object gets initialized
            console.log("FB Object initiated");
            FB.XFBML.parse(); // now we can safely call parse method
       };

</script>