Francisco GP (crishnakh)

When the plugin ACF or ACF Pro 5.6.0 is active the native WordPress Custom Fields on post, pages or CPTs is not visible and gone missing. If you disable the ACF plugin the custom fields are visible again.
The functionality to hide the WordPress custom fields was introduced in ACF version 5.5.13 but then made default in 5.6.0, it was made default to speed up the page speed load of the admin edit page/post screen.
This plugin reverse this behaviour, so you don’t need to edit the function.php of your template.

Custom Fields Missing When ACF is Active

Reverse missing Wordpress custom fields when ACF is activated.

Kenny

The goal of this plugin is to make is really easy for someone on 
Wordpress to implement the NotFound.org missing child page in 
place of their standard 404 page.
The HTTP 404 is the error that you see when a link is broken, 
or you navigated to web page that just isn’t there. It happens, 
and it’s one of the most common error pages you see.
Why not turn that into something that benefits the world? The more 
eyes that see a missing child, the more likely someone could be 
found.
Note: Activating this plugin will automatically replace your 
default WordPress 404 page. To stop it, simply deactivate.
All of the missing child notices are served within an iframe 
pointing to <a href="http://notfound.org" rel="nofollow ugc">NotFound.org</a>.
<a href="http://twitter.com/_kennyk_" rel="nofollow ugc">@_kennyk_</a> for updates, or visit 
<a href="http://codefury.net" rel="nofollow ugc">codefury.net</a>
<h3>Notes</h3>
Because of the current width of the NotFound.org page (720px), it only 
made sense to put it in a separate layout from your site, rather 
then embed it in the current theme. If NotFound.org eventually 
provides a more portable version, I’ll accommodate that too.

NotFound.org 404 Page

This is a Wordpress plugin that turns your 404 "page not found" error into a page devoted to helping find missing children.

Custom Fields Missing When ACF is Active vs NotFound.org 404 Page