Audacity is recording NOTHING!

Long time no see! Nothing else has changed, same operating system and version. I went to make my own version of one of the most watched videos on YouTube, “Build Our Machine”.

However, Audacity is recording Nothing. All there it’s recording is a bit of noise that is very faint. Nothing else. How do I fix this?

[u]Recording Computer Playback On Windows[/u].

Everything is how it should be though!!