[JaTochNietDan]

Two reasons most likely, first of all this

pawn Код:

new randomskins[4] = { // Not sure why you added an extra cell, it's only storing an integer
   29,
   47,
   48,
   285
};

And this

pawn Код:

GivePlayerWeapon(playerid, 24, 99999);
                            GivePlayerWeapon(playerid, 3, 0);
                            GivePlayerWeapon(playerid, 41, 99999);
                            GivePlayerWeapon(playerid, 31, 99999);
                            CopOnDuty[playerid] = 1;
                            SetPlayerSkin(playerid, randa);
                            format(string, sizeof(string), "[LSPD:] %s is now an on duty police officer.",GetPlayerNameEx(playerid));
                            SendFactionTypeMessage(1, COLOR_LSPD, string);
                            return 1;

Is missing the random code, unless you just left it out of the snippet.

There should be a

pawn Код:

randa = random(sizeof(randomskins));

In there.