[SOLVED] Errors in registration and update in front end

I use CB 2.4.0, and now it is impossible to:
- sign up for a new member (he can prepare all the lines of the form, but not register it),
- modify his profile for an old member (he can prepare all the lines of the form, but not register it).
An error message comes always the same like:

--> La session a expiré ou les cookies ne sont pas activés par votre navigateur. Veuillez cliquer sur "Actualiser" et vous assurer d'avoir bien activé les cookies dans votre navigateur. Veuillez rafraîchir la page avant de saisir.

ps: I'm french. In english read "The session has expired or cookies are not enabled by your browser. Please click on "Refresh" and make sure you have cookies enabled in your browser. Please refresh the page before entering."

But, even I apply all these rules, the error is permanent. I use the Firefox navigator with the last version. And it's the same bad result with Chromium.

Did I miss an update or a special new plugin ?
Thanks for your help !

Either something is caching the registration form or something is breaking the cookie. Switch to default Joomla protostar template and see if issue persists. If it does turn off and clear Joomla cache then retry. If issue still persists see if you've installed any extensions that may mess with cookies (e.g. some of the EU cookie notice extensions break cookie storage).

Thanks Kile for your help.
I tried all that you wrote, but without none change: the issue still persists !
Please, what have I to do with the CB parameters in order to do nothing about these cookies ?
Greetings.

This doesn't just break out of the box. Something was installed resulting in it breaking. Review what you've installed and unpublish extensions as needed then retry. Typically 3rd party system extensions or extensions that alter cookies could cause this. Ensure live_site in configuration.php is also set to '' (empty) as you may have domain matching issues in the cookie. You can try disabling spoof checking in CB > Configuration > Integrations, but it is not recommended to do so.

Oh, thank you very much, Kile.
You just saw right about the "configuration.php" file on my site: the "live_site" parameter contained the url of my site !
Now, all is returned fine.
Happy week-end for you.
Greetings