Hi David,
I was having the same problem, but I found when I switched themes the plugin started working as expected.
I’ve experimented using Chromium, Chrome, Firefox, Konqueror & Rekonq.
I have an additional variable in play, which is that I’m using a free, unsigned dreamhost ssl cert, and I found that depending on which theme I used, in addition to your plugin working or not, http would forward to the base WP url, which uses https, or not.
(I’ve since installed the “Easy HTTPS (SSL) Redirection” plugin to cover my bases)
The misbehaving theme in both cases was the minimalist “less”, which I was looking forward to using, but when I switched to Twenty Fifteen, everything worked as expected.
Any idea what might be causing the problem in some themes and not others?
Thanks!