It sounds like you're doing it right.
I just took a little project I've worked on before and recreated it to show you. Look at the screen captures below and see if there's anything different in what I did and what you did. You can see that the slide and buttons preview fine in the EPUB Interactivity Preview panel.
EDIT: Just noticed that you used On Click as your Event. I think it needs to be On Release or Tap. Try that!
CORRECTION: On Click also worked in EPUB Interactivity Preview.
Thank you so very much Steve. Those snapshots are very helpful. I"ll go back through my settings. You'll probably hear from me again, now that I know there is help available. the documentation on the Fixed Layout EPUB is extremely limited out there. I'll be in touch. Again, I thank you.
Hi Steve, just wanted to report that I worked on my publication this evening and all is well. I'm so happy!
Your screen prints helped a lot.
But more than that, I found that the spread where my slide was placed, had become corrupt. No matter what I did on page 10 and 11, would preview a blank white canvas. So I deleted those pages. It worked.
I wanted to thank you for your help. With a little persistence and your helpful guidance, I've pushed through this stage and ready for BIG TIME pubs.
have a wonderful evening.
I'm glad I could be of help. Good luck!