Does it help to right-click on the problem headings and select Continue previous numbering?
1ST EDIT: It may help if you would answer our initial calls for further detail (refer the comments against your question). You also mention and interchange the terms “heading” and “paragraph” in such a way that it is difficult to fully understand exactly what you are doing. Are you trying to obtain numbering against each Heading N style or against the Default Style or Text Body or some other style (perhaps a custom heading or text style)?
My original answer was partly a suggestion as there are essentially two different methods of applying numbering and each will have different results depending on context:
- Creating a nested list (refer Writer Guide v3.6 pp.78-81, 186-187, 215, 230-235).
- Numbering a hierarchy of headings (pp.197-202).
There are other aspects to applying numbering (e.g., conditional paragraph styles, captions, table of contents, and bibliography) but all relate back to these two methods / requirements. If at any point you have use the Creating a nested list option (e.g., styles) to set numbering for headings then you will obtain the context menu I indicated and as shown here. This is a common cause of outline numbering not renumbering as expected i.e., because a list XML coding is being used in addition to the usual heading / paragraph pairing. The fact that this context menu does not display is indicative that you have not used this approach (at least for the heading in question).
This may mean your problem is more serious (unlikely) or it may just be an artefact of using this numbering against a style that has not been defined correctly (likely). As per the suggestion by @mahfiaz I would try clearing the formatting on the entries in question (including any list settings) and re-apply the required style.
2ND EDIT: As a result of examining the source file provided in this post, it is clearer what the problem is and how to fix it. The basis of the problem is that currently the XML code for your headings looks list this (a nested list as I mentioned) and this is interfering with getting it to look like this (a standard outline heading). I recommend using the provided Heading N styles rather than your custom titreN styles. It is likely that some of the settings on the titreN styles have been modified to the point where they now have problematic definitions. You will need to go through your document and for each heading:
- Clear the formatting (Apply Style pull down menu > Clear formatting).
- If after clearing the formatting a leading number is still present, click the Numbering On/Off toolbar button or press F12.
- Apply the corresponding heading style e.g., for titre1 apply Heading 1, for titre2 apply Heading 2 etc.
Once you have done this for all headings you then need to:
- Configure outline numbering (Tools > Outline Numbering…) by changing titre1 to Heading 1 for level 1 etc.
- Click OK.
Your headings should renumber correctly. You can now style each Heading N style as you wish to make them match the original titre entries, just avoid changing the Outline & Numbering tab details.