ShieldConfigurationExtension not working

I created a ShieldConfigurationExtension in Xcode 14.3 with File > New > Target > ShieldConfigurationExtension. This created the extension with all the necessary Info.plist values (correct NSExtensionPrincipalClass, etc.), with the extension included in embedded content in the host app target.

No matter what I try, the extension is not getting invoked when I shield applications from my host app. The custom UI does not show as the shield, and looking at the debugger, an extension process is never invoked.

I am shielding categories like this:

let managedSettings = ManagedSettingsStore()

...

managedSettings.shield.applicationCategories = .all()

And my extension code overrides all the ShieldConfigurationDataSource functions.

class ShieldConfigurationExtension: ShieldConfigurationDataSource {
    
    override func configuration(shielding application: Application) -> ShieldConfiguration {
        return ShieldConfiguration(
            backgroundBlurStyle: UIBlurEffect.Style.systemThickMaterial,
            backgroundColor: UIColor.white,
            icon: UIImage(systemName: "stopwatch"),
            title: ShieldConfiguration.Label(text: "You are in a Present Session", color: .yellow)
        )
    }
    
    override func configuration(shielding application: Application, in category: ActivityCategory) -> ShieldConfiguration {
        return ShieldConfiguration(
            backgroundBlurStyle: UIBlurEffect.Style.systemThickMaterial,
            backgroundColor: UIColor.white,
            icon: UIImage(systemName: "stopwatch"),
            title: ShieldConfiguration.Label(text: "You are in a Present Session", color: .yellow)
        )
    }
    
    override func configuration(shielding webDomain: WebDomain) -> ShieldConfiguration {
        return ShieldConfiguration(
            backgroundBlurStyle: UIBlurEffect.Style.systemThickMaterial,
            backgroundColor: UIColor.white,
            icon: UIImage(systemName: "stopwatch"),
            title: ShieldConfiguration.Label(text: "You are in a Present Session", color: .yellow)
        )
    }
    
    override func configuration(shielding webDomain: WebDomain, in category: ActivityCategory) -> ShieldConfiguration {
        return ShieldConfiguration(
            backgroundBlurStyle: UIBlurEffect.Style.systemThickMaterial,
            backgroundColor: UIColor.white,
            icon: UIImage(systemName: "stopwatch"),
            title: ShieldConfiguration.Label(text: "You are in a Present Session", color: .yellow)
        )
    }
}

What am I missing?