[Finn]

Try this:

pawn Code:

new checkedIP[32];

forward checkIP(name[], value[]);
public checkIP(name[], value[])
{
    INI_String("IP", checkedIP, sizeof(checkedIP));
}

pawn Code:

new filename[13 + MAX_PLAYER_NAME];
format(filename, sizeof(filename), "Accounts/%s.ini", Encode(pName(playerid)));

if(!fexist(filename))
{
    //register request
}
else
{
    INI_ParseFile(filename, "checkIP");

    new IP[32];
    GetPlayerIp(playerid, IP, sizeof(IP));

    if(!strcmp(IP, checkedIP, true))
    {
        //auto login
    }
    else
    {
        //login request
    }
}

Edit: Changed the code once again.