Don’t you call the multicast event from event BeginPlay?
For example, if you make blueprint like “BeginPlay → Multicast → Multicast calls event run on Server” in GameModeBP,
when BeginPlay is called, there are no players spawned, so multicast cannot call any events in clients.
This is because BeginPlay Events of GameModeBP or LevelBP or so on are called before players are spawned.
If your problem isn’t related to this thing, maybe I don’t have knowledge that can help you, sorry.