"The cell or sheet that you are trying to change is protected and therefore read-only. To modify a protected sheet or cell, first remove protection using the Unprotect Sheet command."
This error occurs when the cell or workbook being used is protected, and Report Builder cannot create or update requests in protected cells.
This error can be resolved by unprotecting the sheet or workbook. Go to the Review tab and click 'Unprotect Sheet' or deselect 'Protect Workbook'.