Warning message by Hummingbird usage....

Hi,

Trying Hummingbird I got this warning:

gzip is not working properly:
- Your server may not have the "deflate" module enabled (mod_deflate for Apache, ngx_http_gzip_module for NGINX)
- Another plugin may be interfering with the configuration
If re-checking and restarting does not resolve, please check with your host or open a support ticket with us.

Our provider has confirmed that module_deflate is wel enabled.

HOw to go on?

Thanks!

EDITING:
access is granted.
Another question.. what is the best way to set minify frm Hummingbird. I see some options are not minifying...

Thanks