Font not changing in response to 'zero' feature being enabled

[chimps-ahoy]

sorry if I don't use correct terminology or if this is a mistake on my part, I do not know font stuff well.

I was configuring my system to use this font on Linux (X11), and I wanted to enable the 'zero' typographic feature because I prefer slashed zeros over dotted ones, so I created the necessary configuration files, and verified that the feature was enabled with fc-match -v 'DSE Typewriter AH' Here is the relevant output:

fontfeatures: "onum on"(w) "zero on"(w)

however, neither of the features appear to be working.

I realized while writing this that I am using the autohint version and perhaps the feature is not enabled there? The site said that autohint was mainly meant for windows, but I figured I'd try it because I was planning on using the font at somewhat-small sizes. UPDATE: I did try with the normal font (no AH), and still no luck

thanks for help :)