My headings h1, h2 and h3 will not display on any mobile / iPhone models above iPhone 11.

[SUNSEASOL]

Please can someone help me asap, I am even happy to pay a small fee. As really need to get this sorted.

Headings (h1,h2,h3) do not appear on iPhone devices ranging from iPhone 11 - iPhone 15 Pro Max. They flash once and then disappear forever.

They display perfectly fine on iPad and Desktop and earlier iPhone models. Please can someone resolve asap? It makes my website look incomplete and unprofessional.

I have circled in yellow - where they should appear. 

Using broadcast theme.

Website: https://madsunsea.myshopify.com/