Some assets graphics not shown in game or scene view

I'm attempting some tutorials with a unity project, specifically in the LEGO Microgame template. I'm at the "Add a platform" stage of the tutorials and just noticed that some assets like the crystals or the platforms are present but they are invisible within the game, with only some partial visibility of just an outline if selected in the scene view.

To fix this I've tried reinstalling Unity a few times but the results were still the same. Any ideas? I've attached a screenshot of what I see in the Scene view versus what it should look like.

 

Looks like it is just beyond the blue fog.

To test this, press run and then while it's running, go into the lighting tab and turn off the fog. Does the piece reappear?

 

Thanks for the reply. I ran it and went to where the platforms should be with no fog. The blue space got less blurry but didn't make any of the crystal icons appear among the green sparkles or the platforms where a few of them should be.

Could it be I'm missing the image files for them?

 

Same issue FPS microgame. Half the prefabs are now blue boxes and half show a preview. Blue box assets dragged in will show up in inspector with only transform info and the manipulator appears on screen but no item