Ich scheitere an HTTPS Umstellung einer WP Multisite

RewriteEngine On
RewriteCond %{SERVER_PORT} !=443
RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [NE,L,R=301]
php_value upload_max_filesize 64M
php_value post_max_size 128M
php_value memory_limit 256M
php_value max_execution_time 300
php_value max_input_time 300
# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*\.php)$ $1 [L]
RewriteRule . index.php [L]


.wp-config


<?php
/**
 * The base configuration for WordPress
 *
 * The wp-config.php creation script uses this file during the
 * installation. You don't have to use the web site, you can
 * copy this file to "wp-config.php" and fill in the values.
 *
 * This file contains the following configurations:
 *
 * * MySQL settings
 * * Secret keys
 * * Database table prefix
 * * ABSPATH
 *
 * [url='https://wpde.org/system/user/?userID=5981']@Link[/url] https://wordpress.org/support/article/editing-wp-config-php/
 *
 * @package WordPress
 */
// ** MySQL settings - You can get this info from your web host ** //
/** The name of the database for WordPress */
define( 'DB_NAME', 'something' );
/** MySQL database username */
define( 'DB_USER', 'something' );
/** MySQL database password */
define( 'DB_PASSWORD', 'something' );
/** MySQL hostname */
define( 'DB_HOST', 'localhost' );
/** Database Charset to use in creating database tables. */
define( 'DB_CHARSET', 'utf8' );
/** The Database Collate type. Don't change this if in doubt. */
define( 'DB_COLLATE', '' );
/**#@+
 * Authentication Unique Keys and Salts.
 *
 * Change these to different unique phrases!
 * You can generate these using the {@link https://api.wordpress.org/secret-key/1.1/salt/ WordPress.org secret-key service}
 * You can change these at any point in time to invalidate all existing cookies. This will force all users to have to log in again.
 *
 * @since 2.6.0
 */
define( 'AUTH_KEY',         'put your unique phrase here' );
define( 'SECURE_AUTH_KEY',  'put your unique phrase here' );
define( 'LOGGED_IN_KEY',    'put your unique phrase here' );
define( 'NONCE_KEY',        'put your unique phrase here' );
define( 'AUTH_SALT',        'put your unique phrase here' );
define( 'SECURE_AUTH_SALT', 'put your unique phrase here' );
define( 'LOGGED_IN_SALT',   'put your unique phrase here' );
define( 'NONCE_SALT',       'put your unique phrase here' );
define('COOKIE_DOMAIN', false);
/**#@-*/
/**
 * WordPress Database Table prefix.
 *
 * You can have multiple installations in one database if you give each
 * a unique prefix. Only numbers, letters, and underscores please!
 */
$table_prefix = 'wp_';
/**
 * For developers: WordPress debugging mode.
 *
 * Change this to true to enable the display of notices during development.
 * It is strongly recommended that plugin and theme developers use WP_DEBUG
 * in their development environments.
 *
 * For information on other constants that can be used for debugging,
 * visit the documentation.
 *
 * [url='https://wpde.org/system/user/?userID=5981']@Link[/url] https://wordpress.org/support/article/debugging-in-wordpress/
 */
define( 'WP_DEBUG', false );
define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', true);
define('DOMAIN_CURRENT_SITE', 'www.fichtelberg.info');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);
define('FORCE_SSL_ADMIN', true);
// Eingefuegt 08.01.2021
// Enable WP_DEBUG mode
define( 'WP_DISABLE_FATAL_ERROR_HANDLER', false );
define( 'WP_DEBUG', true );
// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );
// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', false );
@ini_set( 'display_errors', 0 );
// Use dev versions of core JS and CSS files (only needed if you are modifying these core files)
define( 'SCRIPT_DEBUG', true );
// ENDE
/* That's all, stop editing! Happy publishing. */
/** Absolute path to the WordPress directory. */
if ( ! defined( 'ABSPATH' ) ) {
    define( 'ABSPATH', __DIR__ . '/' );
}
/** Sets up WordPress vars and included files. */
require_once ABSPATH . 'wp-settings.php';
/* Multisite */
define( 'WP_ALLOW_MULTISITE', true );
// Enable WP_DEBUG mode
define( 'WP_DEBUG', true );
// Enable Debug logging to the /wp-content/debug.log file
define( 'WP_DEBUG_LOG', true );
// Disable display of errors and warnings
define( 'WP_DEBUG_DISPLAY', true );
@ini_set( 'display_errors', 1 );
// Use dev versions of core JS and CSS files (only needed if you are modifying these core files)
define( 'SCRIPT_DEBUG', true );