Gzip error


i've installed the hummingbird plugin, but i have a problem with the gzip tool.

i'm getting following error: 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

deflate module is installed and running. is there anything else what i have to do?

Kind regards