Explanation
When using MCS to create machines, each machine is activated using the Microsoft Key Management Service (KMS) or Multiple Activation Key (MAK) licensing1. The base image that is used to create the machines must be rearmed before capturing it, and the rearm count must not be exceeded2. If the base image rearm count has been exceeded, the machines created from that image will not be activated. Similarly, if the version of Windows installed on the base image uses MAK licensing, the machines created from that image will not be activated, because MAK licensing is not supported by MCS3.
1: Create machine catalogs | Citrix Virtual Apps and Desktops 7 2308 2: Prepare a master image | Citrix Virtual Apps and Desktops 7 2308 3: Licensing | Citrix Virtual Apps and Desktops 7 2308