There may be something else installed on the site that’s causing problems here. 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 check again. If Jetpack serves the images, then we’ll know that another plugin is conflicting here. You can re-enable your plugins one by one, checking 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. Then check again. If Jetpack serves the images, then you know it’s a problem with the theme, and you can reach out to the theme developer for a fix.
If none of that helps, can you please try pausing CloudFlare as described here?
https://support.cloudflare.com/hc/en-us/articles/203118044#h_8654c523-e31e-4f40-a3c7-0674336a2753
After you’ve paused it, try again to see if the issue persists.
Let us know how that goes.