Why does NetworkServer.ReplacePlayerForConnection not recognize the instantiated object parameter?

So I am trying to create a respawn function for my networked game in Unity3D. The dead character gets deleted, a new player is spawned and visible, but there's an issue. The error "Object reference is not set to an instance of an object" shows up whenever the ReplacePlayerForConnection function runs. I am absolutely stumped and have looked everywhere for answers. If anyone could help I would appreciate it.

Here is my code:

    //Called when the player clicks the respawn button
     [Client]
     public void respawnClick()
     {
         CmdRespawnClick();
     }
 
     [Command]
     public void CmdRespawnClick()
     {
         var spawn = NetworkManager.singleton.GetStartPosition();
 
         if(charSelect.selectedChar == 1)    //If character 1 is selected
         {
             GameObject player = Instantiate(Resources.Load("Characters/Player1", typeof(GameObject)), spawn.position, Quaternion.identity) as GameObject;
             NetworkServer.DestroyPlayersForConnection(NetworkManager.singleton.client.connection);
             NetworkServer.ReplacePlayerForConnection(connectionToClient, player, 0);
         }
         else if(charSelect.selectedChar == 2)   //If character 2 is selected
         {
             GameObject player = Instantiate(Resources.Load("Characters/Player2", typeof(GameObject)), spawn.position, Quaternion.identity) as GameObject;
             NetworkServer.DestroyPlayersForConnection(NetworkManager.singleton.client.connection);
             NetworkServer.ReplacePlayerForConnection(connectionToClient, player, 0);
         }
 
         //Waits for a moment to de-activate the respawn button
         StartCoroutine(WaitForRespawn());
     }