collapsible plugin always comes up uncollapsed

collapsible plugin always comes up uncollapsed

How can I get it to show as uncollapsed (the content is hidden) when the page is loaded. I've tried setting the contentOpen variable, and that does nothing. I also tried doing a trigger click and that doesn't work either. I can manually click on the heading and collapse or uncollapse the content. That's the only thing that works. Has this ever worked for anyone?

I like the one that's for mobile only. It even works on the desktop but messes up the appearance of everything else on the page.