The lack of links from the home page is not the problem. You have a linking structure problem in your site that the xml-sitemap spider cannot follow. I have used xml-sitemaps.com probably a hundred times and have never seen a problem with finding pages unless there is a problem with the site itself. It is also a good tool for troubleshooting problems with linking structures.
Originally Posted by 5starpix
Are you using an unusual linking structure? Stick to the standards for relative links or use fully formed absolute URLs in the hyperlinks.
Are you using redirects for some of the links? If so, get rid of them.
Do you actually have hyperlinks leading to those pages or are they floating pages?
Yes, you can manually enter the remaining 16 page URLs into the XML sitemap, but you should fix the site problem first.
"It's inexcusable for scientists to torture animals; let them make their experiments on journalists and politicians." -Henrik Ibsen