datagridview not updating on screen

I am working on a Powershell script which has a tab control containing a datagridview that is not bound to anything (i.e. database).  The user checks some checkbox columns in the datagridview, selects an Apply button, then I compute some data and update the checked rows in the table programmatically.  The datagridview consists of 3 columns and n rows. Colum 0 is checkbox, column 1 is a name and column 2 is a state.

   I can update the appropriate cell with the command:

$dgvList.Rows[$row].Cells[$STATE_INDEX].value = $newState

However, the screen does not update with the new state.  I have tried several variations the following:

     $dgvList.RefreshEdit

     $dgvList.Invalidate

    $dgvList.InvalidateCell

    $dgvList.Update

Nothing, seems to work.  I have no bound datasource, so I don't need to tweak that.  Clearing all the rows in the table and adding them back in does work to a lesser degree, but feels very inefficient and I lose any selected rows the user may have checked. As it stands, I am still losing any rows that have been checked.

Appreciate, any insight