Hi Kenshin,
Your column data types are different (on data sheet though formatted as number, the values are TEXT).
[C2]=SUMPRODUCT((VALUE(Data!$A$2:$A$806)=Sheet1!A2)*(VALUE(Data!$B$2:$B$806)=Sheet1!B2)*(Data!$C$2:$C$806))
Applied custom formats so the "0" does not show as 00/01/1900 00:00:00: dd/mm/jjjj uu:mm:ss;[=0]""