Why don't my objects reflect in the base plane? I'm clearly missing something basic, and no doubt terribly simple. I've seen videos and tutorials on constructing reflective objects, and kind of even understand them (and I'm at least sure I'm exactly duplicating their material settings).
So, I made a large plane mesh, and gave it reflective material settings. Then I built three objects that I placed just over it (red blue and green). The objects are visible, they cast shadows, etc. But the plane does not reflect the objects.
What am I doing wrong? (Also, apologies if there are random strange characters; they echo right but when I go to the next line sometimes a few characters in the previous line change to random things! Gotta reboot I guess, even on Linux.)
This screen capture shows the material the base plane is made of, and the three objects, and the lack of reflections. That orange line is the edge of the base plane, selected, so the material shown is really the material of the base plane.

I was hoping to upload the whole project (it being trivial and hence small), but that doesn't seem to be an option. Blender version is 2.82.7, running on Ubuntu 20.04.1 LTS.
Check the Ray Visibility settings for each of your block objects.  If glossy is unchecked, you won't see the object in reflections.