Sometimes your internet browser can cache (store) some information in your browser's temporary files or cookies that causes an issue with the reader correctly loading a book. Normally this happens to users have already accessed their ebook at least once before (but not always!)
The solution for this is almost always to clear your browser cache. Instructions on how to do this can be found here: How to clear your browser cache.
If this does not resolve the issue please complete our support form to submit a ticket to our customer support. Please quote your device, the browser, browser version number and the book title in your support ticket. If you can send a screenshot of the reader stuck in this loading state that is extremely helpful.
If after an period of loading an error message appears instead then this is a different issue. Please quote the error message (example: AER59925) when you contact support.