Save, Close, and Reopen your report
Select the clipboard icon to the left of "Edit"
Choose Default Style > Reset Default
After hitting apply, save and close the report. Once you reopen you should be able to then set cell headers.
Save, Close, and Reopen your report
Select the clipboard icon to the left of "Edit"
Choose Default Style > Reset Default
After hitting apply, save and close the report. Once you reopen you should be able to then set cell headers.