Ask for serial number http://forums.adobe.com/thread/1234635 has a FAQ link
Cloud programs do not use serial numbers... you log in to your paid Cloud account to download & install & activate... you MAY need to log out of the Cloud and restart your computer and log back in to the Cloud for things to work
Some general information for a Cloud subscription
Log out of your Cloud account... Restart your computer... Log in to your paid Cloud account
You have purchased CC today, have you signed out & signed back in of the Adobe CC desktop to activate the subscription.
The activation server shows that you have not yet activated the CC though you have an active CC.
Please follow Sign out, Sign in | Creative Cloud Desktop app to activate the CC that you have purchased.