My test worked for the following:
Adding hours to a date field: [Created]+(8/24)
The function DATEDIF(start_date,end_date,unit) says that if the start_date is greater than the end_date, the result will be #NUM!.
So try as follows:
IF(ISBLANK([Authorization Date]),[Receive Date]-TODAY(),[Authorization Date]-[Receive Date])
I created a mockup of your scenario and found there was an issue for me using the Today value and would not actually let me create the calculated formula column, so perhaps that could be part of the issue (although I don't see how it could have been working partially.)
Instead using TODAY() seems to allow the formula to work correctly, at least according to ...
To get the Today date in calculated column, you should use Today() instead of Today.
Besides, you don't have to use AND(),OR() function to wrap your condition. This should work for you:
=IF([Report Completed]=TRUE,"No",IF(ISBLANK([Report Completed Date]),"n/a",IF([Report Due Date]>TODAY(),"Yes")))
If you have 2013 platform workflow, then you may try to create a workflow has a loop which will not end and put a pause 24 hrs action in side the loop. So each time the loop runs will wait for 24 hrs then start the next run