[Mean]

Well.
1. You did a fail here, it will only work for id0.

pawn Код:

public OnPlayerConnect( playerid ) // You must add playerid here
{
    //new playerid; // THIS WILL ALWAYS BE 0
    SendClientMessage(playerid, COLOR_YELLOW,"This server is using neon system by [EDT]Quattro. Use /neonshop!");
    return 1;
}

2. Indentation fails
3. You got some unneeded brackets here:

pawn Код:

public OnPlayerCommandText(playerid, cmdtext[])
{
    new cartype = GetPlayerVehicleID(playerid);
    new State=GetPlayerState(playerid);
 
   
    if(strcmp(cmdtext, "/neonshop", true) == 0)
    {
 
                SetPlayerInterior(playerid,0);
                {if(State!=PLAYER_STATE_DRIVER) // Wtf is that bracket here
                {SetPlayerPos(playerid,-1980.0026,474.2643,29);}
                else if(IsPlayerInVehicle(playerid, cartype) == 1)
                {SetVehiclePos(cartype,-1980.0026,474.2643,29);
                SetVehicleZAngle(cartype,180.1530);}
                else
                {SetPlayerPos(playerid,-1980.0026,474.2643,29);}
                SendClientMessage(playerid, COLOR_YELLOW,"Type /neon in the garage to pick a neon!");} // This bracket too ?
 
        return 1;}

But, atleast it works.