I gave up in frustration for a bit because I have the dream song I've been wanting to play, but it wont show up on the list.
I just tried turning off the real-time protection and running the dll installer but no songs appeared on the list. I just went through all of my cdlc songs' properties tabs and finally found the "unblock" check box. I noticed some interesting things:
1. my old cdlc (pre-taking rocksmith off the steam store) did not have the unblock option.
2. All of my "new" cdlc had the unblock check box.
3. There were songs that I have played that had the unblock box unchecked.
I am rather dense at times, especially when I am frustrated, and I am at my wits end with this lol. Someone said that they had stuff show up in game after a day or so. I'll try checking again in a day or two. If I don't reply to this, assume the problem persists. Also, I did recheck the dll file, it had no unblock checkbox.