[Cjgogo]

Well,as TheDeath specified,I do rely on the fact that at the top of your gamemode you have:

pawn Код:

new seconds[MAX_PLAYERS];

YOU might have forget something very,VERY IMPORTANT,I hope you did not,and that important thing being this:

pawn Код:

public OnPlayerConnect(playerid)
{
   seconds[playerid]=0;
   return 1;
}

I hope you initialized seconds as 0,when player connects,otherwise,that's definetely the problem what's causing the bug.
And in the end,here's a better layout for your timer:

pawn Код:

forward scoretimer();
public scoretimer()
{
    for(new i=0; i<MAX_PLAYERS; i++)
    {
        if(IsPlayerConnected(i))
        {
         seconds[i] ++;
         if(seconds[i] >= 1800)
         {
            SetPlayerScore(i, GetPlayerScore(i) + 1);
            seconds[i] = 0;
         }
       }
    }
    return 1;
}

Hopefully,that works.