public OnRconLoginAttempt(ip[], password[], success)
{
    if(!success)
    {
    }
    else
    {
    new PlayerName[MAX_PLAYER_NAME];
    GetPlayerName(playerid, PlayerName, MAX_PLAYER_NAME);
    SendRMsg(playerid,COLOR2, "You has logged as RCON Adminitrator. Account: %s", PlayerName(playerid));
    }
}

public OnRconLoginAttempt(ip[], password[], success)
{
    if(success) //why (!success) when just (success) ?
    {
        new PlayerIP[16]; //you need to compare the IP, not the name, max IP length is 16
        
        for(new i=0; i<MAX_PLAYERS; i++) //loop through all the players
        {
            if(IsPlayerConnected(i))
            {
                GetPlayerIP(i, PlayerIP, 16);
                
                if(!strcmp(PlayerIP,ip)) //compare the players ip to the login attempt
                {
                    SendRMsg(i,COLOR2, "You have logged as an RCON Administrator. Account: %s", PlayerName(i)); //send the player who logged in a message (and fixed spelling of "Administrator")
                    break; //break out of the loop, you have found the player, so stop looping
                }
            }
        }
    }
    return 1;
}

new PlayerName[MAX_PLAYER_NAME];
GetPlayerName(playerid, PlayerName, MAX_PLAYER_NAME);