Gzip Compression issues with my sites

I am attempting to use Gzip compression as advised by Hummingbird. I am getting the following message:

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

I have looked at the .htaccess file and the code appears to be in place.

Any help would be greatly received

AJ

PS Support access is open if required