Site w/ Addon Domain doesn't show CSS

I have a website with its main domain name and an add-on domain.

When I access the Wordpress site from the main domain, CSS/JS loads without any issues.

When I access the site through the add-on domain, CSS/JS doesn't load, however the links work!

My .htaccess file looks as follows:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>
# END WordPress

Do I need anything else?

Also, my hotlink protection of my site is disabled.

Any help or pointers will be appreciated!!!

Thanks