Complete list not showing in a drop down list from a named row

Hi
I've got a worksheet with a list of 45 Clubs across row 1 and the names of the various teams associated with each club in the column below the relevant club name. I've created a Dynamic Name for the club names with the following in the "Refers to" cell of the Name Manager which I believed would expand the Name selection as more club names are added across the row.

 =OFFSET(Teams!$A$1,0,0,1,COUNTA(Teams!1:1)-1)

I've got the drop down selection list on another sheet, but when I scroll down the list it only show 28 of the team names. The List box is simply Data Validation using the row name (=Dynamic_Clubs ).

Any ideas why I can't see all the 45 clubs in row 1 of the "Teams" sheet in the drop down please?

Thanks

Yes. The Club names run from A1:AS1 Richard.
Looks like it was a simple error of not putting the $ in front of the 1:1 selection.

Thanks again Alpha Frog! Not at all sure why that made the difference but it worked!