If your slider or custom featured posts widget is not working, try this:
1. Go to your blog dashboard -> Settings and check if your blog is set to Private. If it's Private, that's why the widget is not working - the slider uses the blog feed to display posts and when the blog is private, the feed is inactive. As soon as your blog is set to Public, the widget should start working fine.
2. If your blog is Public, but the widget is still not showing up, go to your blog dashboard -> Settings -> Other and make sure "Allow Blog Feed" is set to Full. If it's not set to Full, the widget can't display posts.
3. If you're displaying featured posts instead of recent posts, double-check if the label is written the same way in the code as it is in your post. For example, if the label is written as "Lifestyle" in your post, but as "lifestyle" in the code, that's the reason the widget is not working.
If you're tried everything and the widget is still not working, get in touch with me and I'll check what's the problem.