In standard hi/low games, duplicate cards are losses. That's where the house edge (should) come in.
Unless you are playing war
Sorry, I mean casino card-sharks type games like this. You are betting if the next card is high or low. If you bet that the next card is going to be lower then a ten, and the next card is a ten...you lose, because it's not lower.
It should be outlined in the rules, anyways the game was bugged before hand, not paying people out enough on wins.