503 error on apache virtual hosts

I created a virtual host with the following code on an ubuntu apache server

cd /var/www/
sudo mkdir fd-pro
sudo mkdir /var/www/fd-pro/ch-api
sudo mkdir /var/www/fd-pro/ch-api/public_html
sudo chown -R $USER:$USER /var/www/fd-pro/ch-api/public_html
sudo chmod -R 755 /var/www/*
nano /var/www/fd-pro/ch-api/public_html/index.html

And created index.html

Then

sudo nano /etc/apache2/sites-available/domain.mydomain.com.au.conf

<VirtualHost *:80>
    DocumentRoot /var/www/fd-pro/ch-api/public_html
    ServerName domain.mydomain.com.au
    ServerAlias domain.mydomain.com.au

    <Directory /var/www/fd-pro/ch-api/public_html>
        AllowOverride All
        Require all granted
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/domain-error.log
    LogLevel warn
    CustomLog ${APACHE_LOG_DIR}/domain-access.log combined
</VirtualHost>

sudo a2ensite domain.mydomain.com.au.conf

sudo service apache2 restart

No errors were displayed, but sever responds with 503 error. Can anyone help me?