One of the common problem that most WordPress users face at some point is 404 error on all pages except home page. Usually in this scenario, you will be able access the WordPress admin area, the blog’s homepage, but when accessing all pages except the homepage, you will get a 404 Not found error.
If you encounter this problem, what you need to do is fix your permalinks settings.
Go to Settings » Permalinks, and simply click on Save Changes button.
If this does not work for you, then you probably need to update your .htaccess file manually.