is_user_logged_in() caching issue

I am having and issue with the is_user_logged_in() function (i think).

I have installed the italian version of wp and install a theme that i bought. Followed all of the directions just fine.

They have a check in the header to see if the user is logged in and shows different stuff for logged in users vs logged out users.

I login just fine and the items that are supposed to be shown for a logged in user are shown and then go to the main index.php or / directory of my wp install and it changes the layout like i am not logged in. But if i then ctr+R (refresh) the page it fixes the issue.

Does anyone know what is causing this problem. I can reproduce this on an english wp install…?

Thanks