Hummingbird Errors

Hello, I have successfully run most of the features available in Hummingbird. However, I'm getting an error message when trying to run the GZIP and Caching tools. My host is SiteGround VPS. Can you lend any advice?

Browser Caching is not working properly:
- Your server may not have the "expires" module enabled (mod_expires for Apache, ngx_http_headers_module for NGINX)

gzip is not working properly:
- Your server may not have the "deflate" module enabled (mod_deflate for Apache, ngx_http_gzip_module for NGINX)