css not loading in subdomain sites.

So I have a site example.com that has a wordpress multisite installed.
When I go into the back end of the network everything is fine, however if I go into any one of the sub domains xx1.example.com or xx2.example.com both the front end and the back end don’t load the css or js files.

According to chrome’s dev tools the problem is that the files aren’t found (error 404). This just happened, a few days ago everything was fine.

This is the .htaccess file

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

# uploaded files
RewriteRule ^([_0-9a-zA-Z-]+/)?files/(.+) wp-includes/ms-files.php?file=$2 [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).*) $1 [L]
RewriteRule  ^[_0-9a-zA-Z-]+/(.*\.php)$ $1 [L]
RewriteRule . index.php [L]
# END WordPress