Posts not posting!

Are you getting any errors? Please check your Log/History tab and let me know what do you have there.

They are posting 6 hours later it seems. No errors.

Do you have any delays set?
Do you have WP Cron setup correctly?
https://www.nextscripts.com/tutorials/wp-cron-scheduling-tasks-in-wordpress/

No delays. It was working happily for over a year, and has now stopped.

It was working happily for over a year, and has now stopped.

THis is usually the sign that your WP Cron is not OK.

Do you have WP Cron setup correctly?