Gzip apparently not enabled, but apparently is enabled.

Hi guys,
I'm getting this error from hummingbird about the gzip compression: https://www.screencast.com/t/L9drQe9c
I've been in touch with the web host who have stated that mod_deflate is enabled, and also that a test from http://www.gidnetwork.com/tools/gzip-test.php shows that gzip is enabled.
Running WP 4.9.2 and Hummingbird 1.7.2
Any ideas?