Having trouble animating dropshadoweffect in a style

See more:

XAML

WPF

So frustrated.

Why does this work:

<window.resources>
        
            <Setter Property="Effect">
                <Setter.Value>
                    <DropShadowEffect ShadowDepth="10" />
                </setter.Value>
            </setter>

But this does nothing:

<window.resources>
        
            <Style.Triggers>
                <EventTrigger RoutedEvent="MouseEnter">
                    <EventTrigger.Actions>
                        <BeginStoryboard>
                            <Storyboard>
                                <DoubleAnimation From="0" To="10" Duration="00:00:01" Storyboard.TargetProperty="(DropShadowEffect.ShadowDepth)"/>
                            </storyboard>
                        </beginstoryboard>
                    </eventtrigger.Actions>
                </eventtrigger>
             </style.Triggers>

In other words, I can make a shadow appear statically, but when I animate the same property, no shadow appears when the mouse enters?

Thanks all for taking a peek. This has to be something simple that I am missing.

What I have tried:

I have already tried replacing

Storyboard.TargetProperty="(DropShadowEffect.ShadowDepth)"/>

with

Storyboard.TargetProperty="(Button.Effect).(DropShadowEffect.ShadowDepth)"/>

but this throws a runtime exception.