I found the problem. For some unknown reason, I was working in an extremely huge scale. My model (in real life) would be a couple miles across, but when I measured it, it was millions of miles long! lol
So I scaled the entire layout down, and scaled down again, and again, and I can finally see the textures now (although I will have to do some editing).
Question: does Sketchup work like vector programs? Meaning, can I assume that every element scaled down perfectly and kept its original proportions?

A huge thanks to you guys for taking the time to give your input!

@xrok1 said:

go inside your group or component.

I can't be positive (because I've only been using Sketchup for a couple days) but as far as I can tell, the objects are not in groups. Is there anyway I can check?
Even when I create a brand new rectangle (for example), and try to apply a texture, it does not work.

@takesh h said:

I think you are in "shaded" mode.
Go to menu, select [View]-[Face Style]-[Shaded with Textures].

Just checked, it was in [Shaded with Textures] and I still only see solid color where there should be materials.

I'm having an issue with materials. When I select a material in the Materials window, then click on an object in the scene, the object changes color to something similar to the texture (for example, if I try to use "Brick_Antique" the object just becomes brown, but no bricks are visible). This happens with all materials and in all files.
Thanks in advance!