Excel not calculating

[Usha]

I have 7500 rows of data. I am trying to prepare a
summary of the data into a Summary sheet. I have the
following array formula to achieve this.

{=IF(SUM(IF(data!$A$2:$A$6562=AL$2,IF(data!
$D$2:$D$6562=$A236, 1,0)))=0,"",SUM(IF(data!
$A$2:$A$6562=AL$2,IF(data!$D$2:$D$6562=$A236, 1,0))))}

This doesn't return any value. Column A in the data sheet
has Week numbers (1,2,3 etc) and column D has Severity
levels (1, 2, 3 etc).

If I double click on every cell in the two columns, the
formula works.(I tried this for week 33).

Could someone please tell me why this does not calculate?

Many thanks.