I recently came across this problem again. It was a while since last time. Anyway, the sitemap would not show when placed inside a child master page (a master page that inherit from another master page…just to be clear). After messing with it, I remember what I did last time.
On the child master page, set the AutoEventWireup=”true”. That’s it.
<%@ Master Language="C#" MasterPageFile="~/MasterPage.master" AutoEventWireup="true" ...
I hope am able to save sometime for someone outthere.