Piece of advice. When troubleshooting, I would make your output an epub file to make it easier to see what is wrong. An epub can be unzipped (you have to change the file extension --- so you can examine the resulting HTML files). You can always convert from epub to mobi later if you need to.
First, when using calibre to create an epub/mobi from an odt file, it has to generate html files which when zipped or processed can have a toc. It assumes that you have formatted your .odt file in a way which allows calibre to guess the chapter headings. For help, see: https://manual.calibre-ebook.com/conversion.html#table-of-contents Generally the safest thing to do is to use the h1 tag or to Heading 1 style within LibreOffice or MS Office; generally Calibre can detect that. (You may need to tweak the conversion settings from the Convert options ).
A epub TOC can mean 2 different things in the context of a epub/kindle file: 1)an html page which appears at the front of the ebook or a 2)TOC when you press the TOC icon in the reading system. In your reading app, check the TOC icon to make sure that nothing appears when you press it. If it doesn't, then that is the source of your problem.
(The first kind of html TOC can be autogenerated using a Calibre conversion option: Force use of auto-generated TOC).
There is a tab for MOBI OUTPUT/EPUB Output options in Calibre: make sure the right things are checked or unchecked:
- Do not add TOC to book (make sure this is not checked!)
(generally the defaults are good, you shouldn't have to mess around with them).
In my experience, generating epubs and mobis from calibre is often buggy. I find that using calibre to convert from docx is slightly better than to convert .odt. So you might try converting to docx just to see if it converts properly.
The key thing though is making sure that the .odt/.docx file is properly formatted and styled. You have to use the STYLES provided by ODT/MS Office for the TOC to be created properly. You can't just manually style the headings.
Hope this points you to a solution.
Further Thoughts: I think Calibre is a great application, but I would never rely on it for a published book (I run an indie ebook publishing company).
Instead, you should create a high quality epub (by whatever means), and then use Kindle Previewer to convert from epub to .mobi Important: Download the BETA version of this Kindle Previewer software -- the link is on the right side of that URL.