Thanks for your intervention.
The error message no longer appears.
But it does not display the 'Nouveauté-presentation' module which is called in 'Select Modules' in the 'Actualité' menu link.
While this module if I position it for example in 'footer' it appears well. (so this module is obviously displayed well outside the mega menu)
No, nothing is resolved.
Your old version (Joomla3) made it possible to call up the display of a module (or a position) in the sub-menu.
Currently I can't call a module, there is just the submenu that is displayed but in no case the module I am calling.
Thank you very much for your reply and debugging your Mega menu.
The problem is not completely solved, depending on the type of module it seems that it is not displayed if it is called individually as a module it does not always work, on the other hand when it is called with a position, it works correctly.
I tested on my site.
I would have preferred it to work correctly as before, if possible, the called module is obviously assigned to all the pages of my site to be sure that it is displayed when it is called with your Mega Css3 menu.
Do you think you can do something about it?
(I call a custom Joomla module with Html inside, I leave my configuration with the individual module call, so you can see if it works on the 'Presentation' menu (in French, where there should be have 'news' (the module))