One textformat is not working on Mobile.
It's the Headline Textformat called "Title".
(On desktop it shows 44px, on Mobile it should display at 20px but it doesn't.)
The other Textformats are working on Mobile.
My website is www.sibyllehornung.com
The problem is this Style Attribute inherited from 'span'
It is overriding both Your Desktop and Mobile versions but because it is 44px it seems like it is just mobile, when removed it works correctly
The Title h1 has this span 44px:
Do you have any Custom CSS added or do you know where else you have set a h1 or title to have 44px font size there seems to be a double up somewhere for you.
Best wishes :)
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