Creating 1 sitemap for mulitple installations.

I have a website with multiple installations as follows:
https://www.beachfrontjobs.com/
https://www.beachfrontjobs.com/timeshare-blog/
as well as /timeshare-jobs/ and /links/
I’m also using Google Sitemap Generator plugin installed on every installation.
Using the path of https://www.beachfrontjobs.com/sitemap.xml, how would I set it up so it would display sub pages and sub posts. Now it only displays https://www.beachfrontjobs.com/timeshare-blog and none of the posts.

Hope someone can help.
Dan