I'm trying to configure a privacy zone for my new camera. How to make this work?

In Tapo app I can navigate to Cameras -> Manage -> hexagon log on top right corner -> Video & Display. Here I see "Privacy Zones Off >"

When I tap that I get to a screen with title "Privacy Zones" and selection "Privacy Zone" with an UI Switch next to it. Whatever I try to do on this screen the switch won't move to "On" position. The is no error message or explanation. Nothing happens.

Otherwise the camera and the app work as documented.

I'm using Tapo app 3.1.307 on iPhone 13 and I have Tapo Care subscription for this camera.