BRC was telling us:
BRC nous racontait que :

This is because the Document_New event does not fire when Word first starts.
Try putting code in the Document_New event of the Normal.dot - when you
create a new document, it fires, but if you close Word and start it again,
it does not fire.

Test this with these in Normal.dot.

In the ThisDocument module:

'_______________________________________
Private Sub Document_New()

MsgBox "New!!!!!"

End Sub
'_______________________________________

and this one in a regular module:

'_______________________________________
Sub AutoExec()

MsgBox "AutoExec!!!!!"

End Sub
'_______________________________________

Create a new document before closing Word.
Then Close Word and start it again.

If you want to workaround your problem, put all your code in a regular
module and use something like I did above, but replace the MsgBox line by a
call to your sub in the regular module.