GPIO button plugin query

Volumio Information

Volumio Version:2
Hardware: RPI3B
DAC:JustBoom AmpHAT

Hi. I am trying to arrange a shutdown button by momentarily connecting a free GPIO to Ground. I have installed the gpio-buttons plugin and added dtoverlay=gpio-shutdown,gpio_pin=16 to config.txt , but connecting GPIO16 to Ground has no effect. Does anyone know what I am missing?

I think the default state for GPIO 16 is to be an input pulled to low, which would mean grounding would have no effect.
Also, I think GPIO 3 is normally used for shutdown switches as it also has the ability to wake the pi after shutdown.

Thanks very much Timothy, you are perfectly correct, connecting to 3.3V works.

In case it helps anyone:

gpio-buttons plugin has (apparently not yet documented) shutdown option, no need to edit config.txt
Using GPIO3 for shutdown seems to interfere with AmpHAT audio so pick another unused one
For waking by switch, there is no alternative to grounding GPIO3
GPIOs 9 and above (? to 27) default low, so grounding won’t trigger

The GPIO buttons plug-in has had a shutdown option for a long as I’ve been using it specs.
My little red button here, takes GPIO pin 10 high for shutdown: