Problem with Scheduled Wordpress posts not posting?

Problem with Scheduled Wordpress posts not posting?

Can anyone advise why it would be that for one of my Wordpress websites when I schedule posts I never have a problem but my other two websites that are also Wordpress whenever I schedule a post to publish at a specific time and date they never publish?

I am so confused and wonder why this is? It would make my life so much easier if I could resolve this problem but I just don't know where to start!

Any advice will be appreciated!