when you click the allow button shown at the right of the image in the first post, the watch app should come up, you might want to try force quitting the watch app. or possibly launching the watch app to make sure it's running and then go back to safari and click the link.
it also seemed to work if I downloaded the files linked above to my Mac, when I double clicked, it asked if I wanted to send to my watch, I was then asked on my watch if I wanted to install the face.
Also verify handoff settings, not sure if that's involved here or not, but it seems like something that might use handoff
if that doesn't work, these aren't "new" faces they're just configurations for existing faces.
if you're not able to download them, you can manually re-create them yourself.