Well... I got CSS to work like I wanted on mobile (see screenshot attached), but have NO idea why it won't work on larger/desktop screens. Site is (pw: aril)
https://arianaloren.squarespace.com/
Any help or insight is much appreciated!!
I'm having the same issue as the OP, and my header is not sticky. Please see the first button on: https://gabrielaydeko.squarespace.com/save-the-date (pw: boda).