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
http://helpx.adobe.com/creative-cloud/help/install-apps.html to install or uninstall
Cloud Getting Started https://helpx.adobe.com/creative-cloud.html
Are you being asked to fill the registration form of Adobe.com repeatedly, in that case log in to www.adobe.com, fill in the details & save it
If the prompts appear again Contact | Adobe you should contact Adobe Support for resolution as it shall need some investigation.