Access to Admin Webpage (Redirect does not work)

[sharbich]

Hello, my dears,
i installed FreePBX Utility 16.0.40.4. If I try to access the admin website via the URL: “freepbx.intern.example.de” then I do not end up on the admin web interface. Only if I call the following URL: “freepbx.intern.example.de/admin”. Where can that be? I use the following configurations:

root@dsme01:~# cat /etc/nginx/sites-available/freepbx.conf
server {

    server_name freepbx.intern.example.com;

    listen freepbx.intern.example.com:80;
    return 301 https://$host$request_uri;
}

server {

    ssl_certificate /etc/ssl/certs/freepbx.intern.example.com.crt;
    ssl_certificate_key /etc/ssl/private/freepbx.intern.example.com.key;
    ssl_dhparam /etc/ssl/certs/dhparams.pem;

    listen freepbx.intern.example.com:443 ssl default_server;
    
    root /var/www/html;

    index index.html index.htm index.nginx-debian.html index.php config.php;

    server_name freepbx.intern.example.com;  # don't use _ or FreePBX may complain about referer

    location / {
        try_files $uri $uri/ =404;
    }

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;  # server defaults are good
        fastcgi_pass unix:/run/php/php7.4-fpm.sock;
        fastcgi_param HTACCESS on;  # disables FreePBX htaccess warning
    }

    # disallows the things that the FreePBX .htaccess files disallow
    location ~ (/\.ht|/\.git|\.ini$|/libraries|/helpers|/i18n|/node|/views/.+php$) {
        deny all;
    }

    # from the api module .htaccess file
    rewrite ^/admin/api/([^/]*)/([^/]*)/?(.*)?$ /admin/api/api.php?module=$1&command=$2&route=$3 last;

    access_log /var/log/nginx/access.log;
    error_log /var/log/nginx/error.log;
}

root@dsme01:~# cat /var/www/html/index.php 
<?php
//	License for all code of this FreePBX module can be found in the license file inside the module directory
//	Copyright 2013 Schmooze Com Inc.
//
if (file_exists(dirname(__FILE__) . '/index_custom.php')) {
	include_once(dirname(__FILE__) . '/index_custom.php');
} else {
	$basename = pathinfo($_SERVER['PHP_SELF'],PATHINFO_DIRNAME);
	$uri = (!empty($basename) && $basename != '/') ? $basename . '/admin' : '/admin';
	header('Location: '.$uri);
}

root@dsme01:~# ls -la /var/www/html/
insgesamt 92
drwxr-xr-x 16 root     root     4096 19. Jul 14:52 .
drwxr-xr-x  7 root     root     4096 19. Mai 12:14 ..
drwxr-xr-x 10 asterisk asterisk 4096 19. Jul 14:53 admin
drwxr-xr-x  7 root     root     4096  5. Mai 11:11 bareos-webui
-rw-r--r--  1 root     root      767  1. Feb 2020  dateiupload.php
drwxr-xr-x  9 root     root     4096  8. Okt 2019  elasticsearch-head
-rw-r--r--  1 root     root       16 23. Mai 03:32 .htaccess
-rw-r--r--  1 root     root       53 16. Dez 2022  .htpasswd
-rw-r--r--  1 root     root      251  1. Feb 2020  index.html
-rw-r--r--  1 root     root      612 16. Dez 2022  index.nginx-debian.html
-rw-r--r--  1 root     root      453 23. Mai 03:32 index.php
drwxr-xr-x  9 root     root     4096 24. Mai 13:01 ldap-account-manager
drwxr-xr-x  2 root     root     4096 16. Dez 2022  letsencrypt
drwxr-xr-x 15 www-data www-data 4096  2. Mai 22:55 nextcloud
drwxr-xr-x 12 root     root     4096 18. Dez 2022  phpldapadmin
drwxr-xr-x 12 root     root     4096 16. Jan 2019  phpLDAPadmin
drwxr-xr-x 13 root     root     4096 19. Mai 19:02 phpmyadmin
drwxr-xr-x 12 root     root     4096 23. Mär 2021  powerdns-admin
-rw-r--r--  1 root     root      361 23. Mai 03:32 robots.txt
drwxr-xr-x 13 www-data www-data 4096 15. Mai 2021  roundcube
lrwxrwxrwx  1 root     root       38 19. Mai 14:02 ucp -> /var/www/html/admin/modules/ucp/htdocs
drwxr-xr-x  2 root     root     4096 16. Jul 12:15 upload
drwxr-xr-x 13 www-data www-data 4096 21. Sep 2021  vmailpanel
drwxr-xr-x 13 root     root     4096 21. Sep 2021  vMailpanel

Do you have a tip where the error is?
Greetings from Stefan Harbich