Not able to Group rows or columns

I have attached a copy of an existing spreadsheet and am trying to create both groups of rows and then groups of columns. I am able to do this in the original file but not in this copy. When I select the rows to be grouped (in this case rows 6-10) and hit the Group function under Data nothing happens. I then select the same rows manually from A6 to DG10 and hit the Group function and still nothing happens. The outline symbols never appear.

As mentioned I have been able to do this with the original spreadsheet but not with this one. What am I doing wrong?

I am running Windows 11 Home ver. 10.0.22000 Build 22000. Excel version 2111, Build 14701.20226

So the first question is - how do I attach the file. I keep trying to drag and drop it and that hasn't been working. I have also zipped it but still won't allow me to attach anything.

Any help would be greatly appreciated