[Command] and [Syncvar] don't work!

Hi everyone, I'm having problems with syncvars and command for too long. I would like to create a button that at the time of the click updates the server and returns an increased value on all clients and the server. But he doesn't want to work and I can't understand why.

     [SyncVar(hook = "OnChange")] public float svar; //The length of a game, in seconds.
     [SyncVar] public bool masterTimer = false; //Is this the master timer?
     public Text ttext;
 
     Test gameTest;
 
     void Start()
     {
         ttext = GameObject.FindGameObjectWithTag("Test").GetComponent<Text>();
 
         if (isServer)
         { // For the host to do: use the timer and control the time.
             if (isLocalPlayer)
             {
                 gameTest = this;
                 masterTester = true;
             }
         }
         else if (isLocalPlayer)
         { //For all the boring old clients to do: get the host's timer.
             Test[] tests = FindObjectsOfType<Test>();
             for (int i = 0; i < tests.Length; i++)
             {
                 if (tests[i].masterTimer)
                 {
                     gameTest = tests[i];
                 }
             }
         }
     }
 
     void Update()
     {
         if (isLocalPlayer)
         { //EVERYBODY updates their own time accordingly.
             if (gameTest && !masterTimer)
             {
                 svar = gameTest.svar;
             }
             else
             { //Maybe we don't have it yet?
                 Test[] tests = FindObjectsOfType<Test>();
                 for (int i = 0; i < tests.Length; i++)
                 {
                     if (tests[i].masterTimer)
                     {
                         gameTest = tests[i];
                     }
                 }
             }
             ttext.text = svar.ToString();
         }
     }
 
     public void OnClick(float amount)
     {
         if (isLocalPlayer)
         {            
             if (isServer)
             {
                 svar += amount;
                 print("Il server aumenta il tempo " + svar);
             }
             else
             {
                 print("PASSO");
                 svar += amount;
                 CmdIncreasSvar(amount);
             }
         }
     }    
 
     [Command]
     void CmdIncreasSvar(float amount)
     {
         svar += amount;
         OnClick(amount);        
     }
 
     private void OnChange(float value)
     {
         print("svar cambiata a " + value);
         svar = value;
         
     }