Web: Sticky Header doesnt show on IOS safari

Site: http://oakesroofingmi.com/ (site is responsive)

The sticky header (logo and phone number) doesnt seem to show on any iphone that i tried. On google chrome dev tools using the mobile device simulator, the sticky header shows up after i scroll down on the page. But when i try it on an actual iphone device, the header doesnt show. I also tried switching the agent to iphone 6

Any advice on how to troubleshoot this issue?

i have not tried it with an android because i dont have one.