Change WordPress user roles and capabilities › Forums › Bug Reports › The HTTP 404 Error Return feature does not work with ajax › Reply To: The HTTP 404 Error Return feature does not work with ajax
Try beta version 4.58.3.b1. It’s available from the Download page after login and contains related fix:
Fix: Content View Restrictions add-on: Posts with “Show 404 HTTP error” option were available via AJAX requests.
The single .php file was changed: