Did you assign a linked cell to those checkboxes?
Did you lock those linked cells?
Did you protect the worksheet that contained those linked cells?

ps. You could drop the .select and just use:

For Each cb In sheets("Input").CheckBoxes


Sean wrote:

Would there be a reason why the code below will not uncheck a Checkbox
that is "True" or ticked?

Sub UncheckBoxes()

Dim cb As CheckBox
Application.ScreenUpdating = False

Sheets("Input").Select
For Each cb In ActiveSheet.CheckBoxes
cb.Value = False
Next cb

End Sub

--

Dave Peterson