Due dates on tasks not there

Hi there everyone! PLEASE assist me with this. All was fine and then for no reason that I can fathom the due dates on tasks are not registering. I select the date, it reflects, I save the task and there is no due date on the task list.
I have a bookkeeping business and I run my tasks by due date. It was GREAT to receive the daily tasks list by email showing what's due on the day.
Two emails to support have not resolved the issue. First e-mail stated that the matter had been fixed. Not so. Second e-mail just got the auto-responder. (17th Feb)
Please help!!!