I can’t see the snippets either. But the object that the variable points to is set to replicated right?
If that is already the case… a likely issue is that if you spawn the replicated actor on the server and immediately try to pass a reference to it to the client via an RPC, the actor hasn’t replicated over to the client yet. That’s why the client receives null: the replicated actor hasn’t been initialized yet on the client.
There is a tidy way around this issue, if the idea is that the client needs a reference to the newly spawned actor and react to that. Instead of an RPC, which has this risk of the passed actor not existing on the client yet, you can declare a ReplicatedUsing variable with a function that fires once the variable (and thus the actor it points to) is initialized on the client. So instead of an RPC, the server sets a replicated variable to the spawned actor (or other replicated UObject). Eventually, the object is replicated to the client, which detects that and runs the OnRep function.
// Your client's reaction to variable being initialized goes here
// The server sets this, it replicates to the client and OnRep_MyDog will execute on the client
Edit: What Jackblue says is important too if your object is not a component or actor!