That's the Grid layout issue. In your code, the Card2 was defined in the

<Grid Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="4"...``` 

That's great. But the question is that you reused this specific Row and Column later in your code, which means the Card2 is overlapped, so you cannot click it.

Either adjust the Grid layout to prevent duplication or you may consider using ZIndex.

From the doc,

An element with a higher ZIndex value will be shown on top of an element with a lower ZIndex value.

Set the ZIndex to a higher value to the Grid which contains the Card2 should work,

<Grid Grid.Row="1" Grid.Column="1" Grid.ColumnSpan="4"  ZIndex="9">

Please let me know if you have any questions!