Trouble spawning objects on server in Mirror

I'm new to Mirror, and I'm having trouble getting some basic stuff working. I'm trying to write this GameObject's Update() method so that when the client connects, the object spawns in the server, and then deletes for the client. The GameObject also has Network Identity and Network Transform components. This is my code:

 void Update() 
 {
     clientConnected = GameObject.Find("NetworkManager(Clone)").GetComponent<MyNetworkManager>().clientConnected; //checks whether the client is connected
     if (clientConnected) {
         NetworkServer.Spawn(gameObject, connectionToClient);
         Destroy(gameObject);
     }
 }

While the GameObject deletes correcty, it does not show up again for the clients. I'm not sure if the GameObject is in fact Spawn()ing correctly in the server but just isn't showing up for the clients, or if it's in fact not even Spawn()ing correctly. What am I not understanding correctly?