I am trying to remove some of the padding above and below my header, and I’m able to see my edits in the GP customizer area, but when I open my site in a browser I still see the extra padding (cleared cache, tried multiple browsers).
It looks like your Siteground Optimizer plugin is moving the theme CSS below the CSS generated by the Customizer, which will make it so the Customizer CSS doesn’t do anything.
If you disable the optimizer plugin, it should start working.
With your advice, I looked into the SG Optimizer settings and they actually offer a way to exclude select CSS from their “Combine CSS Files” option. Because we are getting some supposed performance benefits with SG Optimizer, I was reluctant to completely disable the plugin, but adding exclusions for all GP CSS solved the issue! Thanks!