Solution with SUMPRODUCT
It’s easier for me to use SUMPRODUCT in such situations.
Without a title bar, you can simply use:
=SUMPRODUCT((MONTH(Sheet1!D:D)=MONTH(Sheet2!$B$2))*(YEAR(Sheet1!D:D)=YEAR(Sheet2!$B$2))*(Sheet1!E:E="Name"),Sheet1!O:O)
Just replace "Name" with whatever you want.
If you have a header row (or if the column contains any values that are not valid dates), you need to use the array formula within SUMPRODUCT :
=SUMPRODUCT((IF(ISERROR(MONTH(Sheet1!D:D)),Sheet1!D:D,MONTH(Sheet1!D:D))=MONTH(Sheet2!$B$2))*(IF(ISERROR(YEAR(Sheet1!D:D)),Sheet1!D:D,YEAR(Sheet1!D:D))=YEAR(Sheet2!$B$2))*(Sheet1!E:E="Name"),Sheet1!O:O)
(Array formulas are entered using ctrl + shft + enter )
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