Building my Sitemap

I am currently trying to build my sitemap for a multisite at

I have tried using the plugin WPMU DEV SEO and it only creates a sitemap with 1049 urls my website has over 70,000 posts over the 4 site on the multi site.

Does this plugin have limitations on website size?

Also when I try and submit my XML sitemap to google, google is saying that it consist of HTML. Any help here?