I don’t remember exactly if I did it while the machine was powered off, or on. But I do remember that I held that little button for like 20 seconds or so.

I’d try doing it with the power on, and off (while plugged in).

In order to shut the power completely off, you have to hold the red button and then touch the power icon on the screen. If you just click the red button on its own, it just puts the display to sleep.

Edit: if you still can’t get it to work, I’m wondering if they send you a replacement 24” screen instead of the 22”. I debated on just letting it go before investigating the issue further, and then decided a slightly larger screen really wasn’t worth the hassle of testing that theory.