I have problem with ClientScene.RegisterPrefab

Hello,
I have 2 scenes,
in the first i have the network manager and network manager hud where specified the offline and online scenes, here i don’t specified the spawnable prefabs.

In the second, i have a script where i specified the prefab to spawn. Here first to spawn i registered the prefab:

public override void OnStartClient()
{
    base.OnStartClient();

    foreach (GameObject obj in asteroidPrefabs)
    {
        ClientScene.RegisterPrefab(obj);
    }
}

then if isServer i instanciate the prefab and then i spawn the prefab.
The problem is on the client:
I received the error on the client like (on the host the spawn is ok):

Failed to spawn server object, did you
forget to add it to the
NetworkManager?
assetId=d8b3239a5790cd944ad93a8f8effa2b0
netId=6
UnityEngine.Networking.NetworkIdentity:UNetStaticUpdate()

What is wrong?
i following the manual:
https://docs.unity3d.com/Manual/UNetSpawning.html

ps:
i am trying to use ClientScene.RegisterPrefab and don’t the registered spawnable object of Network Manager.

Here there is the project:
https://drive.google.com/file/d/1e2VpyKc59Zid5lXjuVFL8HqBsJWCNAbF/view?usp=sharing

Thanks,
bye

This is a bug (1035798) and has been confirmed. OnStartClient is actually too late for the registration (I think just under localhost conditions or something like that). When you enable Developer Log mode on the NetworkManager, you will see the errors followed by the registration.
The correct way to do it when using HLAPI is calling it in Awake (they said the docu will reflect that in the future)