No Index (ToC) after PDF export

Pretty common question but I haven’t found a solution…
In LibO Version:, on Ubuntu 16.04LTS, after using Writer, creating a Table Of Content through “Indexes and Tables”, using the paragraph styles Heading (n/a,1,2,3,4…)

When exporting to PDF, through quick export or detailed.

The side pane in document viewer does not allow me to view “index”, I can see thumbnails, and annotations and bookmarks are empty.

I used to, using old versions of Writer and of Ubuntu, be able to view and access my index (ToC) in the side pane using the same procedure as what I’ve tried. Allowing me to access different parts of my document by clicking index (ToC) entries…

Any help is welcome

In detailed export there are many options about the export of bookmarks, initial view, links etc. Have you tried them? ex. have you tried Tagged PDF option?