Can't get WP Stack CDN plugin to work

[gbot]

Hi,
I'm at a loss .. it looks so simple, but I just can't get the CDN must-use plugin to work.

I've tried it on 2 of my sites, both running WP 3.9.1. I've created the wp-content/mu-plugins/ directory and dropped the plugin into there.

I've created the CloudFront CDNs, one using a CNAME, the other just using the cloudfront domain, I've also defined the constant in the wp-config.php file -- but, nothing happens?!

One site has W3TC installed (not using the CDN option from there, obviously), the other has no caching. However, when I browse the site, neither has URLs re-written to point the CDN?

I've confirmed that the CDN is working, I can view content using the cloudfront url, and in wp-config.php I have:

define ('WP_STACK_CDN_DOMAIN', 'xxxxxxxxxxxx.cloudfront.net');

Can you offer any help to get this working?

Thanks in advance.

[gbot]

I just realised that I also need to define 'WP_STAGE' -- it's working fine now.

Thanks.