How to get _SESSION vars working?

I have an web-app that uses _SESSION vars and it is done in PHP.

If you go to its page, you simply cannot login to it to see how it looks like and how it behaves
because _SESSIONS vars are lost. The Session Vars are lost just because Envato embeddes the app into its own page that says in the upper-right corner with green “Buy this app”.

I have purchased a SSL certificate so I now have HTTPS://.

Can someone pinpoint me to the right code that would make my app keep my SESSION vars thus being able to show my potential buyers how the app behaves?

Thanks !!!

I think you are mistaken in the source of the problem and incorrectly formulated the question. It is best if you show a specific example of a page with a part of the code responsible for starting and checking the session.

Contact your hosting provider. The problem is related to the server ( PHP Session configurations )