Definitely a Z-code issue, not an ics calendar issue. Other elements are showing on top of the sticky header.
Thanks for the info on where to change the font.
I got it to work by checking the load in AJAX setting.
I just upgraded to Pro and my calendar is not showing up in full style. I can’t find the Load CSS and JS on wp_enqueue_scripts action option in the settings. I only see a checkbox for using the new defaults.