I have been working on a book layout, and today any imported text or image is only coming up as a red dotted outline. Editing within a text frame behaves normally and any already existing text or image can be edited normally. I'm using windows 10 on a Dell XPS
The imported text and images have been placed on to the wrong layer in the document - in the Page & Layer gallery, expand the affected page(s) to show the layers.
You should find that the text and images coming up as a red dotted outline are on the Guides layer, drag them to the same layer, as those that display correctly,in the same page.