[Jstylezzz]

change

pawn Код:

SendClientMessageEx(playerid, COLOR_GRAD2, "You're not in a vehicle!");

to

pawn Код:

SendClientMessage(playerid, COLOR_GRAD2, "You're not in a vehicle!");

and

pawn Код:

if(IsPlayerInAnyVehicle(playerid) == 1 && Seatbelt[playerid] == 0)

to

pawn Код:

if(IsPlayerInAnyVehicle(playerid) && Seatbelt[playerid] == 0)

I have a seatbelt command too, and mines has the above things, which work..