GZIP compression not working using Hummingbirg

Hi guys,
I tried to activate GZIP compression through the Hummingbird plugin. It seems that the missing JS GZIP compression the site gets quite slow .
Activation in the .htaccess file works so far, but I get the error, that the activation itself did not work.
I checked for the mod_deflate to be on (as using plesk I can easily activate these ) and it was active. Restarting apache did not help.
And I'm not sure if and which other plugin would interfere here.

Any ideas?
Thanks and best regards,
Christoph