Here are some of the remedies:

1. The article's permission may be set to private. You may change the article privacy settings by editing the article.

2. If the article's permission is public, the category where the article belongs to may be set to private. You may change the category privacy settings by editing the category.

3. The menu item where your frontpage latest entries is assigned to may have been configured to only show from a limited set of categories. Edit the menu item and select the categories (hold shift key to select multiple) where articles are not displayed on frontpage.