Sticky Header Z-index

Hello, you gave me this solution for the z-index, but it's not working on this site. The sticky header remains on top.
Scroll down so the sticky header appears, and click on a photo in the gallery.
https://jjbhome.com/our-work/kitchens

https://support.balbooa.com/forum/gridbox/17974-sticky-header-z-index-ignite-gallery-popup#85262

Thank you for your assistance on this.

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