Cancelling Scheduled Class

I can start the timer, but I can't seem to cancel it. Can someone tell me what I'm doing wrong? And yes, the cancel() is being reached to, but doesn't seem to be doing anything.

Code:java

public class GameLogic extends BukkitRunnable implements Listener
{
private int countdown = 0;
private Core plugin;
 
public GameLogic(Core coreClass)
    {
    plugin = coreClass;
    }
 
@EventHandler
public void playerJoin(PlayerJoinEvent event)
    {
 
    if(plugin.getServer().getOnlinePlayers().length == plugin.getConfig().getInt("GameLogic.MinPlayersStart"))
        {
        countdown = plugin.getConfig().getInt("GameLogic.CountdownTimerStart");
        runTaskTimer(plugin, 0, 20); //Starts Countdown Timer
        }
 
    }
 
@EventHandler
public void playerLeave(PlayerQuitEvent event)
    {
 
    if(plugin.getServer().getOnlinePlayers().length == plugin.getConfig().getInt("GameLogic.MinPlayersStart"))
        {
        countdown = plugin.getConfig().getInt("GameLogic.CountdownTimerStart");
        cancel(); //Cancels Countdown Timer
        }
 
    }
 
public void run()
    {
    countdown--;
 
    if(countdown == 0)
        {
        cancel();
        }
 
    }
 
}

Rephrase, after doing some print statements the scheduled task does appear to cancel, but I cannot reschedule it. I just get this error.

Code:

Caused by: java.lang.IllegalStateException: Already scheduled as 22

EDIT by Moderator: merged posts, please use the edit button instead of double posting.