Table of Content issue in indesign Book document - epub

Hello, I have an InDesign Book file with 9 InDesign documents inside which I want to turn into an epub. Each InDesign document has its own independent table of content and they all worked just fine. Once I decided to make a TOC  for the book itself, I added the proper paragraph style in each document, however, now only the TOC in the first InDesign document works properly

Once exported, the epub  TOC works fine for the Book and it goes to the correct page in each 9 InDesign document. However, other than the first document, all the other 8 files, the TOC links are disabled. Any help would be much appreciated. Again, in the first document, the TOC links are functional. thank you for your time.

PS

initially I omitted the TOC for the Book, all the TOC links functioned properly in all 9 documents when exported to epub.