SSRS 2008 Sorting Not working

Question

I can't figure out why sorting is not working in my SSRS Report. I have a Tablix on the report that groups by column A.

When I preview the report, Columns B - N have sort handles at the top (little black triangles, one pointing up, one pointing down)

When I click one of these SSRS pretends to sort the data, but when it finishes, the data is still in the original unsorted order. Why?

Edit - These columns are within a grouping. When I take the grouping out, they will sort as they should.

When I try checking "Apply this sorting to all groups and data regions" and setting it to the name of the grouping I get the following error"

The tablix ‘tablename’ has an invalid SortTarget “group_name”. The scope must be the current scope, a peer scope, which is a data region, or an ancestor scope. If the current scope and target scope are groupings, then both scopes must be along the same axis.

What does this mean? I have tried every option in the dropdown and it either results in the error message or the same non-functioning sort I was originally dealing with.

Solution

For the column headers that have the sort triangles, check the Text Box Properties. Under Interactive Sorting, check to see that the Sort by: expression is set as expected. You probably want to be sorting the Detail Rows for "Choose what to sort:"