Since this fix wasn’t working in the child theme I decided to insert the shortcode directly into the theme file /template-parts/content.php.
This worked perfectly in both the top page with excerpts and also the archive page with excerpts (see attached screenshot). To finalize this issue I have 2 questions:
How can I get the Social Share Icons and the “Read More” button on the same line?
Why doesn’t the shortcode work in the child theme but only in the original theme file?
The mistake I was making was to make the changes to a copy of content.php in the sparkling-child theme folder. After making the changes to a copy of content.php in the sub-folder wp-content/themes/sparkling-child/template-parts/, the Social Share Icons are now displaying below the excerpts in the top and archive pages.
The only issue now is to get the Social Share Icons and the “Read More” button on the same line (see screenshot above).