Browser caching and compression with Hummingbird and WPEngine

I've tried to enable browser cache and compression in Hummingbird. It successfully edits the .htaccess file but then it says there is an error on both (see below). We use WPEngine. I've talked to their support and they confirm that both expires and deflate modules are installed and available to use. Any ideas? Thanks!

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)
- Another plugin may be interfering with the configuration

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