NEXTPAGE tag not working

I’m using WP 3.7.1 and would like to try the <nextpage> tag in a few instances.

After composing a post and inserting <nextpage> where needed, everything shows great in the visual and text editors. Looks good in Preview as well.

However, when the post is published the tag does not work. The post stops at the forst incidence and no page numbers show. The remainder of the post is hidden.

Going back to the editors shows that the tag is still there.

Any ideas on why publishing the post breaks nextpage?

Thanks.