Hallo and thanks!
I have tested it today. There is no change. Sorry.
I have installed “WP Control”. Cron jobs are listed. Result ob Post Expirator jobs: “Not responding” and “Cron events trigger actions in your code. A cron event added using the form below needs a corresponding action hook somewhere in code, perhaps the functions.php file in your theme.” “Hook name “postExpiratorExpire”.
I could not find any help in the world wide web for this information. Nothing. I think, a plugin may give information if code must be added at some place. I have learned that this is possible: “Ninja Firewall” is such a plugin, it needs conde in a .php, I have inserted it, and in works.
I learned that wp-cron-job works only when a page or post is called, and problems can be caused by low traffic.
Next step I will try next week: disable wp cron job and install a “real cron job” that calls the cron.php from outside. I hope… and I will post it here.