Tried this on a Pixel 9, after allowing permissions the Start Scanning button does nothing, and there's nothing in the debug log. I do like the idea and might try again in the future if it gets updated. Seems like a good candidate for F-Droid instead of Google Play.
I had to tap the sprocket in the top right and enable Foreground Service to get the button to work
On my Pixel 9 this overlaps the status bar, and can't be clicked. I worked around that by split-screening it with another app.
I'm having the same problem on a Pixel 7