503 Server Error

When I attempt to use this plugin, I receive the following error message when I open the combined JS file:

Error loading script content: http://airadpromotions.com/wp-content/themes/wpthemeairad/js/modernizr.custom.71910.js
HTTP Code: 503 (Service Temporarily Unavailable)

I receive this error for every JS file.

https://wordpress.org/plugins/js-css-script-optimizer/