Magento 2 - Grid UI Component sortOrder Does Not Working
Once you updated your xml to update the sortOrder, but it is not working, maybe it is because of cache or bookmark of the account.
So, the simple solution is to clean up
ui_bookmark table, then
cache:flush, then refresh the page.
Simple way to delete all bookmark is by truncate table :
truncate ui_bookmark. Truncate is the simple way of drop table, and then create new table.