Unable to Edit Cell Placed in Column Header

By default, you cannot edit cells in column headers or column footers. For example, if you place a textBoxCell in the column header and run your project, the cell will be neither selectable nor editable. If you want to allow users to edit cells in the column header or footer, use the settings below.

Set Section.ReadOnly property to False.
Set Section.Selectable property to True.

Also, if you are unable to select or edit a cell, check the following settings.

Set Cell.ReadOnly property to False.
Set Cell.Selectable property to True.

Finally, if the cell type by default does not support user edits, then you cannot provide editing even when you place the cell in a column header or column footer.