I can’t get custom CSS to work on single post.

I am sure i am doing something wrong. don’t really know CSS 🙂

When i add this in the customizer additional CSS it works to hide excepts across the site.

.singular .intro-text {
    font-size: 2rem;
    letter-spacing: -0.0315em;
    line-height: 1.4;
    display: none;

when i add this at bottom of post using your plugin it validates code when i hit publish. yet no change happens and when i go back to edit there is no per post custom css.

I haven’t created any default css in the plugin config as i have no idea what i want there – i don’t want to modify things by default?