You can find here (http://www.mlpa.com/WebForms/WebFormMain.aspx?Tag=_wl2zCji-rCGANQgZPuTixmJ2eZ3fP3MP6xBOEwmgLU9ReUFc8CHQog..) a troubleshooting flowchart. Otherwise, even if you don't have enough DNA in the reaction, at least the control peaks should be visible (see question 8 in the flowchart). If you don't have anything, check the other steps, too.