Hello Stefan,
WOW !!!
Thank you immensely for your help !!!
I was aware that there might be some trouble with me attempting to start my own Theme from scratch, but I was also looking forward to learn new things that would help me greatly in future developments…
It happened exactly as you had imagined, effectively I didn’t have the <?php wp_header(); ?> and the <?php wp_footer(); ?> pieces of code, which in my ignorance I thought weren’t truly important… but now with your help I’ve learned that these are action hooks which must be present, as they provide access to libraries and are used by plugins, like yours.
After adding this action hooks to the header.php and footer.php templates, your plugin now works perfectly with my extremely simple Theme made from scratch…
By the way, I encourage people to start their own themes from scratch as well… it feels good to enter the WP Theme Editor and find ONLY templates which you are actually using, and sometimes it’s even faster to do it yourself than to plunge within some strange complex Theme trying to force it into your design expectations…
Again, Mr. Boonstra, thank you again for your help and basic WP Theme Education, this is a topic resolved !!!
Greetings from Costa Rica !!!