Attached Property in StateTriggers
The demo code like the follow below:
<VisualState x:Name="view720">
<VisualState.StateTriggers>
<AdaptiveTrigger MinWindowWidth="720" />
</VisualState.StateTriggers>
<VisualState.Setters>
<Setter Target="Text.(Grid.ColumnSpan)" Value="3" />
<Setter Target="Text.(RelativePanel.Below)" Value="Image" />
</VisualState.Setters>
</VisualState>
So just add the parentheses around the attached property and it would be worked fine on StateTriggers.