multisite 404 error for subdirectory

I had the axact same problem.

My solution: edited/etc/apache2/sites-enabled/000-default.conf. It needs to look like:

<VirtualHost *:80>

        ServerAdmin webmaster@localhost
        DocumentRoot /var/www/html

        <Directory />
                Options FollowSymLinks
                AllowOverride all
        </Directory>
        <Directory /var/www/>
                Options FollowSymLinks
                AllowOverride all
                Order allow,deny
                allow from all
        </Directory>

        ErrorLog ${APACHE_LOG_DIR}/error.log
        CustomLog ${APACHE_LOG_DIR}/access.log combined

</VirtualHost>

It works!