I just want to offer a quick solution for anyone who happens to share my particular situation and is having trouble with this workflow. This only applies to you if you did a fresh install of Alfred 4 (the app, we aren't talking about your license) rather than an upgrade from Alfred 3.
I got a new mac and used it as a chance to do a fresh install of Alfred 4, which keeps workflows in a different directory than before, breaking several workflows that used to work just fine.
Alfred 3 files:
~/Library/Application Support/Alfred 3
Alfred 4 files: