The game is called Hold Em Poker:

My Cards were: Q J House Cards were: 10 9


Both me and the house can draw three cards from the community cards which were:

7- J-A-8-J


I thought I won with three J. But the store operator put the card into the
Machine and came out no winner.

Did the house cards beat me??

I think a straight beats 3 of a kind.

You got JJJ, house got 7 8 9 10 J, a straight. Straight is the next thing up from a 3 of a kind