I've been using the free plugin for a while but it just stopped working properly.
I disabled all other plugins but that didn't fix it.
The page using the plugin is here https://www.colettehosmer.com/press-2/
If you scroll down to the gallery and click the first item, "Please wait, the application is loading" and a spinning wheel.
If you click the 4th item along the top row, the flip book opens but the pages are blank.
I emailed you privately a couple weeks ago and included access credentials to the website but I never heard back.
If this is something fixed by your paid version then I don't mind buying the plugin.