Font not applying on mobile IOS?

Site URL: https://southernspells.squarespace.com/readings

For some reason, a few text elements are rendering with no font applied on mobile (iPhone). I'm just using standard Squarespace fonts, however I have used CSS variables so that it applies certain fonts i.e. "@subheading". 

Variables

@heading: 'guanabara-sans';
@paragraph: 'proxima-nova';
@subheading: 'proxima-nova-condensed';

CSS for affected areas

.summary-title,
.product-price,
.variant-option-title,
.ProductItem-nav-breadcrumb-link {
  font-family: @heading !important;
}


h3 strong,
h4 strong,
a.product-title {
   	font-family: @subheading !important;
  	text-transform: uppercase !important;
  	letter-spacing: 0.25em !important;
}

Affected areas (screenshot) 

https://share.getcloudapp.com/P8u18jdr

Have you tried assign font with normal CSS yet? To see if variables caused problem?

@tuanphan Unfortunately it hasn't worked when I've removed variables also

5 hours ago, pearler1570048501 said:

@tuanphan Unfortunately it hasn't worked when I've removed variables also

If so, you should contact Squarespace Customer Care, maybe the font has error itself