To print the memory address use %p instead of %s. Try something like this:
UE_LOG(LogVolume, Log, TEXT("AFUOBVolume::ActorEnteredVolume %p is *Other = "), Other);
or:
UE_LOG(LogVolume, Log, TEXT("AFUOBVolume::ActorEnteredVolume %p is *Other = "), (void*)Other);
Greetings.