Jenifer,
Does your ActivBoard have a sticker on the front with a 20 digit Activation Key? If so, that is the serial number that you will use to upgrade your software to the Professional Edition. If not, When the Promethean License Agreement box appears, ensure that you are signed into Planet and that you are connected to the ActivBoard. You will then select the Upgrade Now button and that will take you to the Planet page to generate a professional version license key. (case# 237333)
Thanks!