CSS does not load when accessing the site via HTTPS using Apache reverse proxy

Question

CSS does not load when accessing the site via HTTPS using Apache reverse proxy

Thanks in advance for your help!

I am running Ubuntu 13.1 on an EC2 instance. My application is written in Node.JS (based on NodeBB), and I use Apache 2 as a reverse proxy to establish a secure connection on port 443.

The problem is that when I visit the site via HTTPS, none of the CSS is displayed!

My browser logs a series of errors of these three types:

Failed to load resource: the server responded with a status of 502 (Proxy Error) 
Uncaught ReferenceError: require is not defined 
Failed to load resource: net::ERR_CONNECTION_TIMED_OUT

Here is my configuration file:

<VirtualHost *:443>
   ServerName forum.ligma.com
   SSLEngine on
   SSLCertificateFile /etc/apache2/forum_ligma_com.crt
   SSLCertificateKeyFile /home/ubuntu/.ssh/myserver.key
   SSLCACertificateFile /etc/apache2/combined-ca.crt
<IfModule mod_proxy.c>
    <Proxy *>
     Order deny,allow
     Allow from all
    </Proxy>
</IfModule>
ProxyPass / http://127.0.0.1:4568
ProxyPassReverse / http://127.0.0.1:4568
</VirtualHost>