Hi - I have a Sheet of orders entered in rows, order date is col D and order quantities in columns O through AM (1 product per column, if not required cell is blank). On a different sheet I am trying to sum all the orders for each product / month

I have entered
=SUMIF(MONTH('Sheet1'!$D$6:$D$1008),4,'Sheet1'!O$6 :O$1008)
meaning if the month value in the cell is 4 (April) count any quantity in corresponding cell column O.

What have I done wrong please?

Thanks for looking