Same problem, no solution. The on-screen wizard interface works ok, and the edit page appears on OpenWebif (http and https), but can't be used due to the "child resource" error.
How do I know the version of this plugin, or even whether it is the right one to use? It seems to be authored by "RitzMo"
[Vu+ Duo2, BH 3.0.2, using AutoTimer installed via main menu - plugins, NOT addons]