Generally, if images or fonts are missing or not showing up properly in your Flipbook, the problem goes back to properly optimizing your PDF.
Have you recently uploaded a PDF for conversion to a Flipbook, but notice that text or images are completely missing?
Most often, this is caused by having a PDF that's hasn't been completely flattened. Try using the recommended settings outlined in the 'Optimizing your PDFs' section of the Knowledge Base and re-uploading your PDF to see if that helps.
If that still doesn't work, contact us.