I am working on an ongoing project to produce a document with a lot of embedded photos. I generally work with the latest PortableApps version of LibreOffice (Currently 6.0.3.2). I have had an extended break and when I restarted I found that images had disappeared from documents. So far I have opened two documents. The older and smaller one had numbered and sized boxes where the images should have been - not what I would have liked but manageable as it looks as if the images will be correctly printed. The less old and larger document does not admit to knowing anything about the images and prints empty pages with just the small bits of text; the document’s size suggests that the images are there. Do I need to go back to an earlier version of LibreOffice?
Take a look on the navigator, to see if the images are there. Verify the option to view the images on Menu/Tools/Options/LibreOffice Writer - View is marked.