Resouces.Load returns null

Most common errors out the way:

1. My files are in Assets/Resources

2. My script uses the path relative to the Resources folder

3. I've tried loading it with just "_block_3"

4. I've tried loading it without specifying a type "Resources.Load("_block_3");"

5. I've even tried calling "Resources.Load(string.Empty)", which according to Unity's documentation should return the entire contents of my Resources folder.

In every single instance, Resources.Load returns null, and I have no idea how to progress further.

I'm using Unity 2019.4 LTS.