Dashboards are working, websites are not accessible though

After importing a multisite with WPvivid , the new (target) WP Dashboards work as expected.

However, the websites themselves are not accessible – neither from the Dashboard by “Visit Site”, nor from a browser by entering the URL.

Before importing the site with WPvivid Pro, I tested the new WP site and was able to access a (bare bones) website, both from the Dashboard via “Visit Site”, and from a browser by entering the URL.

Consequently, the problem must be caused by the import. However, I have no idea on how to fix this.

The URL of the source site is: http://chi-gong.net/
URL of the target site ist: https://chi-kung.org/

Any help would be highly appreciated!

Thank you very much in advance.

Thomas

-.-

This is the .htaccess file of the target site:

<IfModule mod_rewrite.c>
    RewriteEngine On
    RewriteBase /

    RewriteCond %{HTTPS} off
    RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]
</IfModule>

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ $2 [L]
RewriteRule . index.php [L]
</IfModule>
# END WordPress

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