Hi - it would be easier if we could see your workbook in a twbx format
have you tried using Ifnull(DATEDIFF('day',TODAY(),[DUE_DT]),0)
The way the formula works it will return the expression if the expression is not Null and the second argument 0 in this case it it is null -
Let me know if that helped
IFNULL(DATEDIFF('day',TODAY(),[DUE_DT]),0) ---------- did not make any difference. problem still persist.
This may work:
DATEDIFF('day',TODAY(),(IF [DUE_DT]<>NULL THEN [DUE_DT] ELSE TODAY()END))