Compression apparently not working

Hi,
First of all: great plugin, thanks a ton! 🙂
I have one issue with it: The compression does not seem to be fully working anymore.
Google PageSpeed Insights tells me to: “Activate compression” and “Reduce JavaScript”
The page size given by pingdom.com was 1.4 MB, now is 2.2 MB (no content changes made!)
Webpagetest.org also shows compression as no longer enabled.

What can I check/do?

Many thanks!

https://wordpress.org/plugins/wp-fastest-cache/