Redirect www to non-www once again

Dear all,

Yes, I noticed several posts on this or similar topic. But I still have a problem with my redirection of www to non-www domain. My .htaccess file looks like that:

# BEGIN WordPress

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTP_HOST} ^www\.(.+)$ [NC]
RewriteRule ^(.*)$ https://%1/$1 [R=301,L]

RewriteBase /

RewriteRule ^sitemap_index\.xml$ /index.php?sitemap=1 [L]
RewriteRule ^([^/]+?)-sitemap([0-9]+)?\.xml$ /index.php?sitemap=$1&sitemap_n=$2 [L]

RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]

</IfModule>

# Stop Apache from serving .ht* files
<Files ~ "^\.ht">
        Order allow,deny
        Deny from all
</Files>

# END WordPress

My .htaccess file works and mod_rewrite works as well (when I put some garbage string before ‘RewriteBase /’ fragment I have a 500 error).

When I try to access https://www.jerror.net I have 404 error. On the other hand https://jerror.net works properly. Could anyone tell me what else could I check?

Best regards,
Rob