Problem with auctex

[me]

Hi all

I've recently updated my emacs to the version 26.0.50.2 (package emacs-
snapshoot for Ubuntu) and since a couple of days, auctex is not 
automatically loaded anymore when I edit LaTeX file (*.tex). Auctex was 
installed from elpa (or melpa I do not remember) and is stored into 
$HOME/.emacs.d/elpa/auctex-11.89.5/. 

If, within emacs, I type M-x load-library <ret> auctex.el and then M-x 
latex-mode, everything is then ok.. Auctex is not required explicitly into 
my .emacs file (as specified into the documentation).

Can you please help me to debug this ? or give me a pointer to a possible 
solution ? Thank you in advance for your help.