Header and Footers not showing consistently in my York template

Hi, I'm having some issues with my company's new website. I added a lot of custom code and now I'm troubleshooting. One of the main issues is that the header and footer are not showing up on any of the supporting pages. I don't want them to show up on the homepage/landing page at all, but I want them to show up on all of the other pages. Is there any custom CSS or anything that might help clear this issue?I've tried adding this snippet to make it work:

header {display: block !important;}

My website is www.themodernbrand.com

Any and all help is appreciated! Thanks.