"Bookmarks" not available

Bookmarks is grayed out and not available. Not sure when this occurred, but I did recently move the book to Dropbox and then moved it back to My Documents on my pc. I do get a message " xxx is not open from the Library, would you like to copy it to the library?" I said yes, which resulted in another copy in My Documents (the original was in a folder within My documents). When I open the book in the new location I still get the same message "xxx is not open...", and the bookmarks are still not functional.