Sometimes it’s possible that the registry keys SerializedMCSKey and SignedSerializedMCSKey in the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS\MCS location are empty after a fresh installation or after reinstalling multicast.
Patience… It took like 5 or 6 hours to get those values populated by SCCM / WDS. I’ve searched for a way to force this, but I couldn’t find anything online. I’ve tried to reboot both machines, without any luck. If you know a way to force this, please let me know.