Thanks for the suggestions. I tapped the ends of the pop up and I don’t see more options in the books I want to translate.
I first encountered this problem in the middle of reading a book in French. I had been using the translate option occasionally to translate some sentences to English, but then the translate option disappeared. I just bought a book in Spanish and am having the same problem.
Weirdly, some books in English are showing the full options menu in the popup as before and when I click on translate, it translates to Spanish. In both general settings on the iPad and in the Books app, the default language is set to English. Other books in English are just showing the limited menu (without the translate option). This is very strange.