Render displays solid view objects I am running Blender 2.91.2 on Ubuntu 20.10 'Groovy' using Cycles with graphics card GTX 1070 (driver version 460.32.03, CUDA Version 11.2)
The top Viewport image (in the Animation tab) is meant to be the Material view but reflections have been rendered, the second image is under the Rendered view which displays only Solid properties.  I have not used Blender for years but it seems that selecting 'Rendered' shows 'Solid', and selecting 'Material Preview' shows 'Rendered', and selecting 'Solid' shows 'Material Preview'.
The viewports are not as important as the actual render, which I run from the command-line after closing blender.
$ blender --background 333puzzleArray-6-short4render.blend -a produces an animated solid view, uploaded to https://youtu.be/NPvrTFzeML8
What is happening is that material shading, by default, uses a pre-supplied HDRi image as the world (that is why you see some trees and blue skies reflected on the glossy surfaces).
Rendered shading uses the actual settings for the scene, by default just a flat color.
You can set material view to use the actual scene lights and world.

Or you can set an HDRi to be used as environment texture on the world and that would be used for rendered view and to render the scene as well.