Horiziontal Tabs displays as blocks stacked on top of one another

Thank you for your work on this module.

I've spent 2 days trying to get Horizontal tabs to display spread across the top of the page instead of being stacked one on top another on a node edit page.

I meticulously followed the instructions in the documentation. I created a horizontal tab group (htabgoup) and, immediately under the htabgroup, I created horizontal tab items and under the items I dragged my fields. However, when I view the node edit page, none of my fields show up (see attached screenshot1).

Strangely, when I remove the the horizontal tab items from under the horizontal group field, the horizontal items are displayed stacked on top of each other (block display) instead of spreading across the top of the page. I've attached both the manage field setup screen shot and the results.

To ensure I understood the concept, I was able to setup vertical tabs and accordions on the node edit page with no problem. However, the horizontal tabs just won't play nicely.

Please tell me what I may be doing wrong. Many thanks.