Header Won’t Quite Stick on Mobile

Hi – love the idea of this plugin, but I can’t quite get it to work.

I am trying to have the header sticky on mobile only on https://www.thetenyardline.com. I believe I have all the settings correct (I get no errors in debug), and I have tried Legacy and Dynamic with no luck. The header just won’t stick. It ever so slightly bumps down at the moment it looks like it’s supposed to stick, but then everything just keeps scrolling as normal, and the header scrolls up like usual. No sticking.

Any tips or help would be greatly appreciated.