Support

I cannot reproduce this. Does any other option in the .htaccess Maker appears to have the same issue?

Literally any option on that page and tell me if your selection stays after you save.

We think we’ve found the cause. Admin Tools has a safety check: if your site’s configuration.php has the $live_site variable set, and it’s set to a full URL(e.g. https://www.rouchenergies.fr) rather than just being empty, the .htaccess Maker automatically disables the “Redirect www and non-www addresses” option and resets it to “Do not redirect” every time you save — regardless of which direction you pick. This is by design, to prevent an infinite redirect loop between the .htaccess rule and Joomla’s own URL handling when $live_site is hard-coded.

Could you please check your configuration.php file (in your site’s root folder, accessible via FTP or your host’s File Manager) and tell us whether it contains a line like this:

public $live_site = 'https://www.rouchenergies.fr';

If that line is present and not empty, that’s what’s preventing Admin Tools from saving the redirect setting. In that case, the fix is not in Admin Tools — you’d need to either clear the $live_site value (set it to '') or leave the www/non-www redirect handling to be done outside of Admin Tools, since Joomla itself is already enforcing a single canonical URL via $live_site.

Please let us know what you find in that file so we can confirm this is indeed the cause.

If you have $live_site you cannot use the non-www to www redirection (or vice versa). Joomla FORCES the domain name in the $live_site. You can't use the non-www to www redirection in that case, which is why your setting is not applied; it is forced to Do Not Redirect as any other option would break your site.

As for HTTP 421, that's the first time you mention it in this ticket. Go to Configure WAF, Request Filtering, and check the Allowed domains option. Try emptying it.