Why can’t I Add files to my iTunes Library?

I tried in iTunes, choose File > Add to Library but nothing happens. I tried to drag/drop the file into the iTunes window but that doesn’t work either. BTW by window I mean my list of songs (my music Library) the grid, since I don’t see any other windows. Oh, I tried also to choose other media in the menu: “Movies”, “TV shows”
beside “Music” but nothing works.

I did click on “Recently added”
in music, video, TV shows and there’s nothing there.

UPDATE:
While I was fooling around and opening everything, I did click on another “Recently added”;

There’s two “Recently added”: one under “Library” and it’s the very first one on top, and the icon looks like a calendar (a square with 16 little squares) and there’s nothing there. And the other “Recently added” is under Music Playlists and the icon looks like a wheel with 12 “teeths”. See picture.

And what do you know? In that one, there’s 42 videos! What is strange is that I see not only the one I added a minute ago (a 3 min video clip) but all the videos (well many) that I downloaded with Clipgrab.

This is what I do with Clipgrab: I download and once it appeared on my desk (when finish) I put it in a folder on my desktop, where I keep all the videos from YouTube in nice separate folders (Comedy/music/films, etc).

I see in iTunes, clips I never added to iTunes. Clips I downloaded 6 months ago! Clips that has nothing to do with music. How do they come there? And why 42? They are not the last 42 because I downloaded others (one in fact two days ago) that I don’t see here.

Again, what I see on iTunes now are videos. (mp4). I still want to have the songs only.

I see these videos only if I click “Recently added”. I do NOT see them anywhere else (in Videos or Film or Music). How can I move them to the music playlist as audio only (mp3 or mp4)?

P.S: I posted a similar question but don't see how to edit or delete the other. So I posted a new one, more updated.