Gzip in Nginx not compressing

Hi, guys

I have an issue in nginx ubuntu 16.04 in digital ocean.
It seems i configued everything fine in my nginx.conf, but still the compression does not happen.

Here is the situation posted in DO community.
https://www.digitalocean.com/community/questions/enabling-gzip-compression-guidance-needed

Thanks for any help.
I am using Hummingbird Plugin.