I added a Google Custom Search to my website several weeks ago, and it has been unable to find anything other than the home page of my site.
I have manually submitted a sitemap to the custom search, and to the webmaster tools (which for some the custom search can't find, but it says I should add one).
I understand there are not a lot of details here, but I don't have much to go on. I've double checked my robots.txt, there's nothing there that's preventing the indexing of my pages.
EDIT: Actually, does the google custom search work any differently than a regular google search? I assumed that it indexed separate from the regular google search, but I guess it's possible that both a google custom search and the normal google search draw from the same pool of pages. In that case the only way to get custom search to find my pages is to get Google to crawl them...which pretty much makes the custom search useless if it can't find the most recent things I've posted.