CSS Not Applied

I’m just testing out this plugin. I’ve been using JetPack solely for the Edit CSS feature, and I’d like to eliminate JetPack so I’m looking for alternatives.

I have Simple Custom CSS installed, but when I copy the JetPack CSS into this plugin and deactivate JetPack, none of my styles are applied. I don’t see any other required steps in the documentation or mentioned in this forum. Can anyone point me towards what else is needed to get this plugin to work?

Thanks!

https://ww.wp.xz.cn/plugins/simple-custom-css/