[MellowHammer]

pawn Код:

if(!(PlayerInfo[playerid][pAdmin] >= 1)) return SendClientMessage(playerid, COLOR_NOAUTH, "You are not authorized to use this command.");

If you look closely, you can see that you make it so players with admin level 0 receive this message.
not >= 1 is 0 or less. That is why normal players can't use /o.