I had this issue in 2.6.2 but updated just now to 2.7.0 in case it was fixed there, but no joy.
When I create a table and add columns, checking the “sortable” checkbox appears to make the column sortable until the page is saved and switches out of edit mode. Once you save the page, the column is no longer sortable.
Is there a .ps1 file somewhere that has the definitions of pages in code? Or are pages persisted in the repository?
OK so confirmed it’s a deeper problem than just persisting to the XML. I set Sort=“true” on the first two columns by editing the XML, and the page still doesn’t render the columns as sortable: