I have solved this problem. Please, WordPress, jump in here and correct me if I am wrong but I believe I understand this now…
The scheduled posts are caused to be published by something called wp-cron, a feature in wordpress that emulated the scheduled tasks or cron functionality of the operating system. Because wordpress is essentially a php script, not a running application, it cannot do anything that is not triggered by a request to load a page. So WordPress built in something that checks on every page load whether there are tasks that ought to be done or not.
In order to execute the wp-cron, as a page is loading, it must peform an asynchronous request to the server to load the wp-cron script(s). It determines the request based on the General Settings configuration of “WordPress address (URL)” to construct an http request to that site. So, I assume somewhere in the wordpress code there is a “wget $address/cronscript.php” or something like that.
It is possible your hosting server cannot access itself in that manner. For example, our servers are running multiple websites and are behind a firewall that maps an external ip address to the server. If you are sitting on a server at 10.10.10.25 that has a public address of 84.123.81.25, for example, when you try to get content from 84.x.x.x, it may not allow this because it requries going out and coming back through the router. If you are not running internal DNS then when you look up https://www.yoursite.com, you will get the external address. So the scripts in wordpress will fail to ever connect or load.
My solution was to modify the /etc/hosts file on the local server to define https://www.mysite.com as 10.10.10.25.
Now this is a bit technical, I know, but if you manage your own server, you can check this situation for yourself by trying to web browse to your site from the machine your site is running on. If you can do that, then this is not your problem.
If you are going through a hosting provider, maybe you can show them what I’ve described here and it will make sense to them. I happened upon the solution after noticing snarky comments from a WordPress person about how your hosting provider might not have DNS configured “correctly” and that made me think “why would wordpress need to access itself?”
If you are managing your own servers, the consequence of all this is that you need to ensure a local http client can access the “hostname” specified in “WordPress address (URL)” You need that address to resolve (DNS) and you need the ip address it resolves to to be routable to the local host. So maybe if you don’t want to mess with the hosts file, you can tweak your router/firewall? If you have a loadbalanced server array, then you need to realize that wordpress is going to be doing this. There might be more security issues that peopel have in place locally–that might prevent http access to the local server.
If you have command line access to your server, use wget to test whether you can load the hostname.
I hope this helps everyone. It ended months of annoyance for me!
