If you have anything that installs polkit actions in /usr/share/polkit-1/actions/ then polkit.service needs to be restarted to pick those changes up.

I haven't checked the boot order yet, but it may require a change to the systemctl files as well.

My use case was I tried to install 1Password and have it use system unlock (e.g., polkit) and it wouldn't see the action. Since I just learned about polkit today, this took a while to debug. ;-)