Calc: sort not working (Ubuntu 16.04)

I’m selecting numbers a range of selected cells in column AG, and I want it to sort and carry the sort across all other columns for that range of selected rows. I click Data → Sort, which shows sort key 1 is AG. When I click OK it looks like the selected numbers blink briefly as sort, but then they return to same original values.

Build ID: 1:5.1.6~rc2-0ubuntu1~xenial3
CPU Threads: 4; OS Version: Linux 4.13; UI Render: default;
Locale: en-US (en_US.UTF-8); Calc: group

Perhaps the sheet is protected? If possible, please upload an example document to a site such as Dropbox and then edit the question to add the link. Or, give complete instructions to reproduce the problem starting from a blank document, as described under guidelines for asking.