I link to the following url with the included parameter to temporarily change the theme to my site. it works like a charm. But when I leave the browser open for a few mins, it deactivates and I am sent back to the theme that is set in the General Settings for the site. I have come to realize that somewhere, there is a time set that deletes the session cookie that is forcing that change. I need to know how I can either pragmatically extend that time by editing some file in whmcs, edit a setting in php to force that change for the whole site, or activate some configuration in the general settings or configuration files to make that time limit longer. What is the best way to accomplish this?
https://www.mywebsite.com/whmcs/index.php?systpl=theme2