Power Off Doesn't change GPIO - Trying to turn stereo on/off

First off, excuse the boneheaded ignorance in the post. I'm only mildly techie.

I have a rpi 3b running Picoreplayer and LMS. I'm trying to get it to turn my stereo on and off. I've set the GPIO-Poweroff setting in the Tweaks page to GPIO 17 and active low. I plan to run it to a switched extension cord that will turn on w/ ~3VDC. That part is working. But...

When I hit the on screen (right, I've connected a touchscreen and am running Jivelite) "Power Off" button the screen goes black but the pin still still runs 3VDC. I can see that the red rpi light on the board is still lit, so I guess the "Power Off" button doesn't power off.

Is there a way that I can get the "Power Off" button on the touchscreen menu to activate/deactivate the switched power cord?

Thanks!
Andrew