Shepherd Games offers you YUNO, a nice local multiplayer card game with AI support and three game modes.
When did you try to use it? You should click on the UNO button when you have two cards in hand and before throwing on of them card.
When you have only two cards left, before throwing a card, you should first click on the UNO button and then throw the card. If you throw a card and click on the UNO button, it is a penalty.
No worries. Thank you for playing our game. :)