Able to Access Secondary Site but not the Wp Admin Folder

Dear WordPress Gurus,

My main site is https://preview.nationalfed.com/

I created a new site at the following url https://zh.preview.nationalfed.com/

When I tried https://zh.preview.nationalfed.com/wp-admin/, it says my admin panel cannot be found.

The following is my htaccess configuration

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# 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]

I suspect it could either be a DNS Wildcard issue or my htaccess is missing something.

Thanks for your kind help!