You cannot use dequeue because the return cell is a new instance of the cell and not the cell displayed.
Your are two way for change the button state.
Transport your (IBACTION)method in your custom cell class and not in controller class and release legacy code. If you need to update data between CustomCell and controller create and invoke a delegate.
The second way is to reload the Cell of UITableView after setting necessary values for presented the well state
solved How to disable a buttons in a custom cell?