SSRS Expression does not work

I have SSRS expression that works in other report with little differnt in values and  that works fine. When i am trying to use the same in a different report it doesn't work for some reason, Just not sure why.. Am i missing something ? When ever i put the middle nested iif or swap either of it , it doesn't work but if i only have two iif conditions 1 and 3rd it works fine.

thoughts

=iif((Fields!Revised_SOW_Need_By_Date.Value =""  AND DateDiff("d",cdate(Fields!SOW_Need_By_Date.Value),Today())>=7),"Red",
iif(Fields!SOW_Need_By_Date.Value="","Yellow",
IIF(RowNumber(Nothing) Mod 2,  "CornflowerBlue", "White")))