AR Environment Probes in 4.21

I’m trying to follow this article :AR Environment Probes in UE4 4.20 | by Joe Graf | Medium

because i’m trying to make environment probes to work. I make mirror material in order to see if reflections work, but the material always renders black. I’ve attached print string after GetAllARTrackedEnvironmentProbes node and it seems all the time returns 0.
i’m attaching screenshot of my Level Bp setup.

Imgur