Hi mega,
You should not need any PHP code to use the shortcodes of the plugin.
At this point, we request you to switch to some default WordPress theme, then create a brand new page, deactivate any and all page builders and add the shortcode to a newly created page.
Turn on the WordPress debug log before you add the shortcode to the page. If it does not work (as expected for now), start deactivating other plugins one by one after each deactivation and check the page on front-end.
At last, if you get it working and found a conflict with another plugin or theme, please share the name and version of that. Otherwise, share the debug logs related to our plugin.
Because you will be making various changes, it is always good to have a backup (of files and database), in case something goes wrong.