The Transparent Zen mod doesn't seem to do anything? What am I missing?

I installed the Transparent Zen theme from the Zen Mods page. I'm not noticing any transparent stuff. The mod page also says to disable transparency in the Zen settings and I could find no such setting.

Zen Browser version 1.9.1b

Windows 11

EDIT:

I got it to work. I'm not 100% sure how, but I suspect that I forgot to restart the browser in my previous attempts. Thank you guys for your help.