Why doesn't my iPad mini show as a device in iTunes?

I just got a new iPad mini and was planning to sync my iTunes library to it. I've never had issues with syncing my iPod and I understand how to sync and choose playlists. BUT: when I connect my iPad to my computer, the iPad never shows up as a device detected by iTunes. ALSO: It will not allow me to copy over any music manually. I would prefer to not use iCloud, as the iPad and the iPod are the only Apple products I own. I have already downloaded my purchased iTunes onto the iPad, but really would like to grab some of my imported files as well!

The only thing to note: when I last logged into iTunes on the computer, it found an update. However the update did not complete and gave me an error. I've tried multiple times to update it, but it keeps erroring out (does not say what the problem is). Other than this, could there be any reason why iTunes on my computer doesn't detect my new iPad mini??