User is getting 'cannot sort using unknown attribute' error in Users page.
This issue is seen because a column that was selected in the column list is no longer a valid column for the artifact. Please try the following troubleshooting:
1. Navigate to the Users page.
2. When the red flare error message is seen again, please click on the "x" in the red flare box to close it.
3. Select the "Columns" button as seen in the screenshot attached to this case (redflare1.png) and unselect all column names except User Name (this is required)
4. Click the "Apply" button to apply the changes.
5. Click on the User Name column a couple of times to sort on it.
At this point, you can go back to the column picker and select the columns you need to add.