Sumproduct using date range

I have the following formula that is giving me a #VALUE! error and I'm not sure why.

=SUMPRODUCT(--(Overdue!$A$2:$A$2000=$A6),--(Overdue!$F$2:$F$2000>=C1),--(Overdue!F2:F20000<=C2))

I need it to count the number of reviews for each department that fall within the given ranges.

See attached for a sample. All Depts is the sheet I'm working in...All Depts - Answer is what I need it to come up with.

Thanks in advance!