Countif statement doesn't work on some rows

I am trying to count the number of occurances that Yes appears in a Row here
is my code - =COUNTIF(AE2:BL2,"Yes")
If I look in the function dialog box it gives me the correct result i.e. 1
but when I press enter it goes back to 0. I have copied this formula down to
the other rows and out of the 8 rows it works for 2 of them.
Note: I am pulling my data in the worksheet from another workbook into this
one using the INDEX and MATCH feature, on each cell I have a "Formula refers
to an empty cell" message so not sure if this is problem.

~Thanks in advance for any response