When you upload the PDF of your e-book content to Plezi, it ends up being stored on Google Cloud.
On rare occasions, your content may not be available on the cloud, leading to an error message.
The server was not available at the time of import;
Your DNS records were not finalised at the time of import.
Try to reload the document again by going to "Options --> Edit".
If the problem persists, don't hesitate to contact our Support team on the chat :)