Hello, I had this problem when I tried to schedule a post.
But now I figured it out.
There is nothing wrong with cron job or wordpress update or something.
When I tried to create new post. I forgot to select post category. Then I missed my schedule. After I found that problem, I created post with selecting category.Then all good.
I think problem is solved. Please try to select category when you are creating post.
Please reply.
Thank you.