Problem of synchronisation when a server only and clients whereas OK when A host and some clients

[glad fulcrum]

Hie: I want locals players to change some of their properties and inform server that will synchronise the relative player in the others players scenes. I did that with comman synchvar and RPC and it works very well when I have a host and some clients.
But when I have a server only and some clients the synchronisation is haveing errors.

I spend a lot of time trying to figure out what's happen.
Here the error I get on the client:
RPC Function System.Void PhyControllersNameSpace.M_Sail::ClientSetSailOnBool(System.Boolean,System.Boolean) called without an active server.

I do not succed to find the problem
Does someone have an idea where this problem comes from?

All my best and thanks for help

[stable sparrow]

you're calling that from client context

[glad fulcrum]

Hie: I have a sync var (CoG for example) with a sync direction: "Server to Client" and a Sync mode :"Observer") The local player change the Cog using a keybord key, then a Command is called by the client local player to change the color variable on the server.

[Command]
void CmdCoG(float OldValue, float NewValue)
{
CoG = NewValue;
}

as the variable is declared with a hook
[SyncVar(hook = nameof(ClientCoG))]
public float CoG;

the RPC ClientCog is called by the server on the other client
[ClientRpc]
private void ClientCoG(float OldValue, float NewValue)
{
CoG = NewValue;
}

This works perfectly if I have a Host and some clients, but raise errors if I have A server only and some clients.
The error raised is RPC Function called without an active server.

Do you have an idea on the reason?
Thanks for your kind help

[glad fulcrum]

Sorry I do not anderstand

[stable sparrow]

The SyncVar hook cannot have [ClientRpc] over it

[SyncVar(hook = nameof(ClientCoG))]
public float CoG;

private void ClientCoG(float OldValue, float NewValue)
{
    // Do something with NewValue
    // Do NOT set the SyncVar again here...it's already set
}

[Command]
void CmdCoG(float NewValue)
{
   CoG = NewValue;
}