I've been having the same problem, even after trying to reinstall the mod from other sources. Having a poke around in the mod's files, it seems like some of the variables aren't properly set and some of the guests have gotten mixed up so the game is sending you to the wrong person or some people are being tagged as already been served when they haven't.
I'll see if I can fix it, although as I don't have the actual RPGM tools, it'll be fairly slow going as I'll just be using a normal IDE.
In related news, the files show that there should be two main sex scenes with Masterson in the Rich House. One of them you get from talking to him (the "Masterson sex Minigame") while looking around the house, but there seems to another one that you get after saving one of his maids but I have no idea whether that is the maid in the bathroom or the maid in the main hall. Are there any guides around on how to get the various scenes?