Hi there,
Your Jetpack connection is looking good so the problem is not there. But it could be because of any different plugin/your theme.
The quickest way to figure out if something is interfering is to test for a theme or plugin conflict. I know it’s less than ideal, but could you please try the following:
Temporarily deactivate all the site’s plugins except for Jetpack and clear your browser’s cache. Then try checking the slideshow again. If it works, then we’ll know that another plugin is conflicting here. You can re-enable your plugins one by one, trying checking slideshow in between, until you find the one causing the conflict. You can leave it disabled or reach out to the plugin developer for a fix.
If disabling plugins doesn’t help, it may be the theme. Temporarily switch your theme to a WordPress default theme like Twenty Twenty-One. Then try checking the slideshow again. If it works, then you know it’s a problem with the theme, and you can reach out to the theme developer for a fix.