The crawlers follow the links to get to the next pages.
This is one of the reasons why the SEO people work with menus and often create top and bottom menu.
Guideline states: 'Ensure that all pages on the site can be reached by a link from another findable page.'
After that you might want to:
- create a sitemap
- create your robots.txt
Thirdly, there might be a plugin enabled at your side that prohibits them to do this. Please check your plugins.
