i'm not using a dedicated server for my game - so one client is playing directly on the scene of the server.
So he needs to register his vehicle on all connected clients. This works fine, so the SynchronizeCreateMessage is send and the clients, which create the vehilce on their scene.
But after this there are nor synchronization messages send from the server to the client and the client displays the following message "Unable to find object: 1 on client"…
is my approach ok (if yes how could i solve the problem?) - or should i use a dedicated server??
Dedicated server is typically a good idea for separation of duties if nothing else. You need to rely on someone to be authoritative and although one of the clients can be, it's generally best to have that completely separate.