A family of Microsoft word processing software products for creating web, email, and print documents.
I think the error message is misleading because you cannot clear a Content Control checkbox with setting Range.Text to a zero length. You also cannot clear DropDown Lists or Combo Boxes by attempting to clear a text range.
Your code should look something like this:
Private Sub CommandButton1_Click()
Dim aCC As contentControl
For Each aCC In ActiveDocument.ContentControls
If aCC.Type = wdContentControlCheckBox Then
aCC.Checked = False
ElseIf aCC.Type = wdContentControlText Or aCC.Type = wdContentControlRichText Then
aCC.Range.Text = ""
ElseIf aCC.Type = wdContentControlDropdownList Or aCC.Type = wdContentControlComboBox Then
aCC.DropdownListEntries(1).Select
End If
Next aCC
End Sub
Hope this helps