I have two worksheets that are identical in the same workbook

=SMALL(IF(MATCH($R$4:$R$39,$R$4:$R$39,0)=ROW($R$4: $R$39)-CELL("Row",$R$4:$R$39)+1,$R$4:$R$39),AO5)

works just fine on the first worksheet as an array formula

But
=SMALL(IF(MATCH($R$4:$R$39,$R$4:$R$39,0)=ROW($R$4: $R$39)-CELL("Row",$R$4:$R$39)+1,$R$4:$R$39),AO5)

Doesn't work on the second worksheet as an array formula

What am I doing wrong??