Find out if you have access to the Adobe activation servers.
If you see two Adobe logos, you have access to the activation servers. Try signing in to your application.
Creative Cloud applications use your Adobe ID to sign in – not a serial number. If a Creative Cloud application prompts you to enter a serial number, try the given steps to resolve this issue.
If you are experiencing issues related to expired volume serial numbers for Creative Cloud for enterprise, see this article for more information.