Have you seen the help page here?: https://make.wordpress.org/support/user-manual/content/posts/schedule-a-post/ It says:
“Scheduled posts will be triggered by the first visit to your blog on or after the exact date/time you set. If you see that the scheduled time has come and gone and your post has not published, simply log out of WordPress and view your blog’s front page. Your visit should cause the post to appear.”
This sounds like a problem with wp-cron.php malfunctioning or being disabled! You can use Advance Cron Manager to determine what is causing the issue. If that does not help I would suggest talking with your hosts. Some hosts disable cron jobs on shared accounts.
Please let us know if you have resolved the problem… and if you have please make the thread resolved for us!
Thank you.