Fixing CS1061error on NetworkList gets Null Reference Exception

I'm trying to shuffle a deck of cards for multiple players in Unity 2021.2.14f1 When NetworkManagaer.cs looks like this:

  public NetworkList ShuffleOrder;
     . . . 
     private void Awake()
     {
         . . . 
         for (int i = 0; i< 99; i++) { ShuffleOrder.Add(i); }

         for (int i = ShuffleOrder.Length - 1; i > 0; i--) { 
             swap = UnityEngine.Random.Range(0, i);
             c = ShuffleOrder[swap];
             ShuffleOrder[swap] = ShuffleOrder[i];
             ShuffleOrder[i] = c;
         }
     }

...and the players' scripts look like this:

      public void Shuffle()
 {
     int swap;
     CardInDeck c;
     CommonCard thisCard = new CommonCard();
     for (int i = FullDeck.Length - 1; i > 0; i--)
     {
         swap = NetworkManager.ShuffleOrder[i];

         c = FullDeck[swap];
         FullDeck[swap] = FullDeck[i];
         FullDeck[i] = c;   

... I get the dreaded "'NetworkManager' does not contain a definition for 'ShuffleOrder' ..."

If I remove the ShuffleOrder code from NetworkManagaer.cs and change the players' script:

         for (int i = FullDeck.Length - 1; i > 0; i--)
         {
             swap = UnityEngine.Random.Range(0, i);
             c = FullDeck[swap];
             FullDeck[swap] = FullDeck[i];
             FullDeck[i] = c;
 
             NetworkManager.ShuffleOrder.Add(swap);
 
 

    

There is no syntax error, but at runtime I get " NullReferenceException: Object reference not set to an instance of an object" on the ShuffleOrder.Add

I would be very happy to find a fix for either problem.