Hummingbird Minification not working

Hi there,

I am using WPMU Hummingbird plugin. The minification feature is not working. I am getting an error when I try to minify my CSS, JS files.

The error says,

"It seems that we are having problems in our servers. Minification will be turned off for 44 minutes

cURL error 6: Couldn't resolve host '"

I have attached a screenshot of the error. We have had this error for over 24 hours now.

Could you please help me fix this error.