Lottie File Export Failing

VERY newbie here, so I apologize in advance for my inexperience.

When I export to Lottie, the images show as the broken link images, but animated. The HTML file plays fine.
This is, I think, a fairly simple, 5-second animation using 5 imported PNG files. Nothing fancier than position changes, skewing and rotation. I also tried a test using just one of the images and used only movement from one place to another. Same result.

Am I doing something wrong?
Screen Shot 2022-04-14 at 9.38.20 PM