Why can't I access the font editor for list sections

For some reason I am unable to adjust the font size for the text that appears in list sections. I can change the heading, but nothing else. I have been on to tech support and they have made suggestions like updating my browser, turning on and off my wi-fi etc but nothing works. I even tried created a brand new Squarespace account and test site, and I still get nowhere. I tried my laptop too, no joy. I know in the section editor I can set S/M/L /XL in the style menu, but I should be able to assign different paragraph styles to the text in the Font editor.
Can anyone suggest why this is happening to me on my sites?

Oh my God, thank you so much!!! I completely missed that - and so did Squarespace support! I knew it had to be something stupid. Thank you 🙏🏻