What you'll do: let Bookbndr build your table of contents automatically instead of using one typed into your Word document.

Why use the automatic one
If your Word document already has a typed table of contents, Bookbndr marks it as Excluded — because its own generated version is better for an e-book:
- every entry is a working link a reader can tap,
- it always matches your final chapter structure,
- in the print PDF it shows accurate page numbers.
A hand-typed contents page can't do those things in an e-book.
What to do
On the Chapters step, leave any detected "Table of Contents" heading set to Excluded. If you un-exclude it, Bookbndr shows a reminder suggesting you keep the automatic one.
The generated contents is controlled on the Matter step, where Table of Contents appears as a front-matter section you can turn on or off and reorder. See What is front matter & back matter?.