if or and and countif

Hi, I would like to count if the values in Col A of Sheet 1 if they appear in Col A of sheet 2 but only if the Date in Col B of sheet 1 is >= B1 of Sheet 2.

=IF(Sheet1!$B2>=Sheet2!$B$1,COUNTIF(Sheet2!A:A,Sheet1!$A2),"Other")

I want to say "other" if the values in Col A Sheet 1 don't appear even if the date in col B is greater that B1 of Sheet 2

As you can see in the attachment, from C31 down a 0 appears rather than other - can anyone recommend a way to sort this?

cheers for looking