in excel using a rank and ifcount formula shows div/0! as result

in my updating results spreadsheet i am using the formula in cell I6
=IF(H6="","",RANK(H6,$H:$H)+COUNTIF(H6:$H6,H6)-1)
this works perfectly to rank and not show blanks for column H.

When I want to use the same formula for subsequent column's in the same spreadsheet ie N and T the result is DIV/0!.
any suggestions?