Can’t get plugin to function

I’m using a theme called Kadence.

I have tried leaving the FSM “Featured image caption” field blank and putting text in it as well.

Hi Patrick
I cannot see the website, it says I have to be logged in as a user who has permission to view this site.
In any case, if you’re using the default kadence theme, it cuts anything below the maxium height of the featured image (so the caption is actually there but not shown). You could try to use the theme customizer options and set the featured image position on “Above” (at blog posts>single post layout) and add a custom CSS similar to this one:

.wp-caption.featured .wp-caption-text {
    position: absolute;
    bottom: 0;
    background-color: #FFFA;
    width: 100%;
    margin: 0;
    padding: 10px;
}

In the vanilla theme I tried, it puts the caption over the image bottom, but you may need to tune it to your theme colors and styles.

Thanks for getting back to me so quickly!
The code worked very well. Thanks so much.