I have this problem from a while, I have tested the Hummingbird plugin on 3 different servers and same result, after a cPanel update I have noticed this problem.
Gzip is not working properly:
- Your server may not have the "deflate" module enabled (mod_deflate for Apache, ngx_http_gzip_module for NGINX).
- Contact your host. If deflate is enabled, ask why all .htaccess or nginx.conf compression rules are not being applied.
If re-checking and restarting does not resolve, please check with your host or open a support ticket with us.