Leaving a chapter or page title blank triggers the automatic generation of default text for the Table of Contents. If you are relying on these auto-generated titles, you will want to make sure that the chapter field for all of your chapters is completely blank. When this is the case, you’ll see Chapter Title appear in the chapter header information in gray letters:
However if this is not the case, you may have invisible characters or spaces in the title field preventing the auto-generated titles. In this case, when opening your chapter, you’ll see something like this:
To correct this you’ll want to click on the chapter title field above the cog, and use the backspace and delete keys to remove any characters in the title field. Once everything is removed, you’ll see the gray place-holder text appear.