there is no serial number used with cc subscriptions. you use your adobe id to activate your software.
open your cc desktop app and sign out and then back in using the same adobe id used to subscribe to cc, Sign out, Sign in | Creative Cloud Desktop app
That the thing, when I use Creative cloud to open the muse app, I automatic directed to Adobe applications manager, and it also want me to sign in, and when I do, that app ask for att serial number for Muse. what can it be for problem?
Ask for serial number http://forums.adobe.com/thread/1234635 has a FAQ link
A chat session where an agent may remotely look inside your computer may help
Creative Cloud chat support (all Creative Cloud customer service issues)