Genius is unavailable for the song:

So it seems that after the 8.1 update, one thing is always destined to be broken for me. When I updated iTunes last night, the iTunes Genius Sidebar toggle button and View menu item were unselectable. They were greyed out and I had no way of bringing the sidebar back even after changing my Genius settings. So, I AppZapped iTunes and reinstalled like I've done in the past. Now the Sidebar works perfectly. Aside from ITMS listing unrelated artists in the ‘Also by this artist’ section.
Anyways, now my problem is that when I go to use the Genius playlist function, it results in the error ‘Genius is unavailable for this song: blah blah’, so I do as it says and update Genius. Afterwards, that song will work, but none of my other songs do until I update Genius again after trying to use them. I have 45.12GB of music alone, I am not about to go through and manually select each one, attempt to use it with Genius, then update Genius.

It was working perfectly last night when my sidebar was broken. I've already tried unchecking and rechecking all of my music since it seemed that was recommended in other topics, but that did nothing to help. I've switched Genius off and back on. Still nothing. I really really want the option back and working correctly. It's running fine on my work computer and it makes picking music depending on my mood a much simpler task.