Quick answer: Unreal newly-joining client missing a dynamically-added component? Components added post-spawn don't replicate unless flagged - set CreationMethod = Native and bReplicates = true.
Server adds a tag component to an actor at runtime. Existing clients see it; clients joining later don't.
Set CreationMethod
Comp->CreationMethod = EComponentCreationMethod::Native;
Comp->SetIsReplicated(true);Required for late-join replication of dynamically-added components.
Or pre-add at spawn
Add the component on spawn; modify state via replication. Late-join clients see the component as part of the spawn replication.
Verify with the network profiler
net.PrintActorReplicateInfo. New client's spawn payload should list every replicated component.
“Replication of dynamic components requires explicit opt-in. Static components are easier.”
Avoid dynamic component addition in netcode-critical paths. The bug surface is large; the benefit is usually small.