Issue Changing (without www prefix) to (www prefix)

[Alaa Mansour]

hello everybody
iam using Nginx, and the prefix is currently set to (preferred prefix: None), but iam using the domain (example.com)
when i try to change it to : www
i get this error :

The page isn’t redirecting properly

An error occurred during a connection to example.com.

This problem can sometimes be caused by disabling or refusing to accept cookies.


iam using: Additional Nginx directives:

rewrite ^/.well-known/host-meta /public.php?service=host-meta last;
rewrite ^/.well-known/host-meta.json /public.php?service=host-meta-json last;
rewrite ^/.well-known/webfinger /public.php?service=webfinger last;
add_header Strict-Transport-Security "max-age=15768000; includeSubDomains; preload;";

location = /.well-known/carddav {
    return 301 $scheme://$host/remote.php/dav;
}

location = /.well-known/caldav {
    return 301 $scheme://$host/remote.php/dav;
}

location = /robots.txt {
    allow all;
    log_not_found off;
    access_log off;
}

# Enable gzip but do not remove ETag headers

gzip on;
gzip_vary on;
gzip_comp_level 4;
gzip_min_length 256;
gzip_proxied expired no-cache no-store private no_last_modified no_etag auth;
gzip_types application/atom+xml application/javascript application/json application/ld+json application/manifest+json application/rss+xml application/vnd.geo+json application/vnd.ms-fontobject application/x-font-ttf application/x-web-app-manifest+json application/xhtml+xml application/xml font/opentype image/bmp image/svg+xml image/x-icon text/cache-manifest text/css text/plain text/vcard text/vnd.rim.location.xloc text/vtt text/x-component text/x-cross-domain-policy;

location ~ ^\/(?:build|tests|config|lib|3rdparty|templates|data)\/ {
    deny all;
}

location ~ ^\/(?:\.|autotest|occ|issue|indie|db_|console) {
    deny all;
}

location ~ ^\/(?:updater|ocs-provider)(?:$|\/) {
    try_files $uri/ =404;
    index index.php;
}

# Adding the cache control header for js and css files

location ~ \.(?:css|js|woff2?|svg|gif)$ {
    try_files $uri /index.php$request_uri;
    add_header Cache-Control "public, max-age=15778463";
    add_header X-Content-Type-Options nosniff;
    add_header X-XSS-Protection "1; mode=block";
    add_header X-Robots-Tag none;
    add_header X-Download-Options noopen;
    add_header X-Permitted-Cross-Domain-Policies none;
    add_header Referrer-Policy no-referrer;
}

location ~ \.(?:png|html|ttf|ico|jpg|jpeg)$ {
    try_files $uri /index.php$request_uri;
}

and Additional configurations directive:

opcache.enable_cli=1
opcache.interned_strings_buffer=8
opcache.max_accelerated_files=10000
opcache.memory_consumption=128
opcache.save_comments=1
opcache.revalidate_freq=1

[php-fpm-pool-settings]
env[PATH] = /usr/local/bin:/usr/bin:/bin

can somebody help me please?
thanks