Welcome to the community and thanks for posting, Mark!
If you’ve had SharpTools.io open on your Fire Tablet open for a while, you’ll need to manually refresh the browser/page to pull in the newest features.
Keep in mind that tiles flow left-to-right, top-to-bottom and will reflow based on the browser width. The following topic has some tips on designing a dashboard for a tablet from a PC:
How To: Designing Dashboards for a Tablet from a Laptop / PC - #2 by josh
You might also be interested in the new Scalable Dashboards - Fixed Number of Columns feature that we’re working on. Send a note to @support and I’d be happy to get you added to the beta. 