Jetpack Related post not showing

But when i go to appearance – customize i see the related post. but when i close the customizer the related post gone.

You will indeed always see Related Posts in the customizer, as a preview of how it could look on your site. The Related Posts displayed there are examples.

On your posts, however, we try to pull real Related Posts. That does not quite work on your site, because when querying for Related Posts we get the original post back instead:
http://kabar-aneh.com/misteri/domba-aneh-warga-afrika-panik/?relatedposts=1

Compare this with what we should normally get on a site using Related Posts:
https://jeremy.hu/jetpack-remove-the-share-counts-from-the-sharing-buttons/?relatedposts=1

Do you use a caching plugin that may cache pages with a query parameter? If so, could you check your caching plugin options to avoid doing that, thus returning related posts for those queries?

If you do not use such a plugin, I would recommend that you get in touch with your hosting provider and ask them if they have a caching layer in place on your site, such as Varnish, that could return cached pages.

I hope this helps.

I see that you’ve managed to solve part of the problem; the caching issue is now gone and Jetpack is able to query for Related Posts:
http://kabar-aneh.com/misteri/domba-aneh-warga-afrika-panik/?relatedposts=1

Unfortunately, no posts are returned right now. Could you try to install and activate this small plugin, by going to Plugins > Add New > Upload in your dashboard:
https://github.com/automattic/jetpack-addons/archive/public-related-posts.zip

Once you’ve activated the plugin, try to relaunch a full synchronization of your posts with WordPress.com. You can do so thanks to the ‘Full Sync’ button appearing at the bottom of this page, after picking your site from the site picker.

If the Related Posts start appearing, you can deactivate and delete this small plugin.

Let me know if it helps.