I had the same problem - found the solution!! I was trying to change the reference of the month of the pivot table to a dynamic cell of mine, in this case 9, for September. I experimented with referencing other portions of the getpivotdata formula to a different cell. I did it with the formula parts that refer to a word, in this case "Direct", and the formula worked. So i thought maybe it had to do with text. So i formatted the next cell to text, then typed in my problem reference, which was the number of the month, in this case 9, and voila - it worked!!!!