There are two likely causes for your Flipbook to hang on the preloader.
Check your hosting or with your webmaster if your webserver is Microsoft IIS.
If your web server is Microsoft IIS
It may be that your IIS server is not configured to serve .json files. We would advise passing the following information to your webmaster or IT person as they should be able to resolve this quite easily. Ensure that the .json file extension MIME type has been correctly configured in your IIS settings:
File extension: .json
MIME Type: application/json
When this has been done, please clear your browser cache and view your online flipbook.
If it’s another type of server or you have already performed the steps above.
Try re-uploading your Flipbook to your hosting. It may be that an error occurred or a brief network problem caused a file to become corrupt.
If you manually upload, ensure that you upload each file and folder within your project to the server.
If the problem persists please contact the Support team with a link to your Flipbook so that we may diagnose the problem quickly.