Hi kristienVR,
It seems like you have install the software using Creative Cloud Desktop apps. Please use CCP 1.4 to create the package and install it on the users machine. It should not ask for serial no afterwards.
You can download the CCP from https://licensing.adobe.com
You can also refer to this link http://helpx.adobe.com/creative-cloud/packager.html
Please let me know if it helps.
Regards,
Abhijit