If the "Digital Cinema Package" option (the Xport plugin) is not visible in the Custom settings drop-down menu within Compressor, in spite of the installation of Xport having succeeded without error, the problem is most likely due to the user not having rights/permissions for the folder LIBRARY>APPLICATION SUPPORT>APPLE QMASTER into which Xport is installed.
The solution is to enable permissions for this folder. The cause for permissions no longer being available is most likely an automatic update to the OS.