3D Prefab Not Showing In Scene and Game View While in Hierchy

Hi all,
I have yet to run into a problem like this and could not find appropriate solution online.

I have a project with both 2D and 3D assets. I've just downloaded the 3D Modern Menu 1 from the assetstore and all of the sudden, all the 3d prefabs from other asset demo scenes stopped appearing. 2D demo scenes shows up fine but 99% of the 3D prefabs would not show at all.

I checked the layer settings and they are all in correct form - on Default and on Visible.

For the life of me, I can not figure out what the issue is, please help.