I'm pretty sure it's because you're using EOSOURCE and their EO+ system sucks? Because I remember using scripts like this and having them working all the time, until I loaded them on EOSOURCE. Try doing something like this:
State State4
{
        desc        "Return To Cujo"
       
        action     AddNpcText(26, "Omg, You did it!!!");
        action     AddNpcText(26, "You dont know how proud of a man you've made me!");
        action  AddNpcInput ( 26 , 1 , "Give items to Cujo" );
        rule    InputNpc ( 1 ) goto Reward1
}
state Reward1
{
        action     RemoveItem(491,10);
        action     GiveItem(1,1000);
        action     ShowHint("You have received 1000 coins from Cujo.");
        rule        GotItems(1,1000) goto EndState
}
/// And As Apollo Mentioned ///
state EndState
{
action End();
}
If that doesnt work, change the second state to this:
    action     RemoveItem(491,10);
        action     GiveItem(1,1000);
        action     ShowHint("You have received 1000 coins from Cujo.");
        action     AddNpcText(26, "Here is your reward. Enjoy yourself!");
        rule        TalkedToNpc(26) goto EndState