Did you add a template?
I successfully installed this add-on on my heavily-modified store.
I currently have these other mods installed:
Simple Visitor Newsletter with HTML Support
Activation Code
Newsletter Unsubscribe
Points and Rewards
Thanks to Olof Larsson for his hard work!
One thing he didn't mention is that many email providers strip certain html and css elements from emails. For example, background images.
By the way, there was an error in the forgot password file. $REMOTE_ADDR doesn't work, but that's an easy fix ;]
If you want me to install this for you, pm me and we can talk.