[Hummingbird] Error: Gzip is not working properly, may not have the "deflate" module ena

When I try to activate Gzip, I get the 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).

– 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.

I contacted the host (Hostinger) who confirmed that all those modules mentioned are indeed installed but suggested that there is probably a plugin incompatibility responsible for this. I disabled many of them but found that this is an exercise of futility as I would have to do this on tens of websites. I rather dump Hummngbird (which gives me countless errors, anyway and is responsible for most of my website crashes and its minify functionality just doesn't work with the Enfold theme, full stop. Unless you spend hours and hours trying to tweak it) than spend hours to find the offending plugin.

But maybe you can?

I have granted support access to the site.

Thanks in advance.