Header font size not responsive on Safari using calc formulas. Scales as expected on Chrome but not safari.
Thanks for writing to us.
I checked your given site URL in Safari browser of iPhone 7 plus. It seems that the font size is responsive and working fine at my end. It might be the issue of your browser cache or your browser is not updated. Please clear your browser cache and then check it again.
Please have a look at the screenshot given below.
If I miss something please let me know with marking screenshot.