It looks like you are mixing and matching properties and components.

To my knowledge "apower" is a property of for example a "Switch" component in the Pro 4 PM. See https://shelly-api-docs.shelly.cloud/gen2/Devices/Gen2/ShellyPro4PM

So "Switch.GetStatus" will get properties including apower, voltage and current.

There is a separate voltmeter component for the shelly sensor add-on - though not used on any of the base devices I am aware of. The voltm

For these types of items make sure to always double-check the documentation for the device you are working with.

For example the Shelly Pro 4 PM - does not have voltmeter as a component. Rather it has voltage, power and current as properties of the SWITCH component.

When in doubt "Shelly.GetComponents" should list all the available components on the device.