When you say they aren't being crawled, is the status "discovered not crawled" or not even "discovered"? Sitemaps only get you so far, especially when a significant number of new URLs have the same overall URL structure & content. Google may have crawled some and didn't see any value in crawling all the others if they looked like doorway pages or didn't have enough content that would be considered helpful for users.
Internal linking also plays a big role - if you aren't linking to it and demonstrating that it's an important page for users to access on your site, then that could be another signal that they are built for search and not users.