New User Question - Sort by Column greyed out

For a pie chart you do not use the 'Sort by Column' button. You need to add the SORT field to Tooltips from Fields on the right.

Because it's a sort column you may need to set the field to Average (rather than Sum) or the order will be wrong. To do this click the dropdown to the right of the filed name once it's in the ToolTips box.

Then on the Pie chart use the drop down elipsis (...) top right to set that field as the sort order.

Also, if the pie seems to show the results in anti clockwise order you need to change your sort order from 1-10 to 10-1 as the Pie Chart shows the largest value first (as most people want to show the largest revenue first).