There are two likely causes for your Flipbook to hang on the preloader.
These steps may also fix any error codes: 406 in the iOS or Android Flipbook Viewer app
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 or .xml files, or may not be serving them correctly. 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 and .xml file extension MIME type has been correctly configured in your IIS settings:
File extension: .json
MIME Type: application/json
File extension: .xml
MIME Type: application/xml
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.
This can also be the cause of another problem regarding text disappearing when zooming into your flipbook. Please ensure that the mime type for SVGs is configured as image/svg+xml.
If the problem persists please contact the Support team with a link to your Flipbook so that we may diagnose the problem quickly.