iTunes not recognizing CDs

Hi. iTunes is no longer recognizing CDs inserted in either DVD drive of my computer. I just upgraded to the latest version of iTunes 12 last week, but I'm not positive I've ripped a CD since 12 came out. I've tried the following:

Clicking on the concentric circles icon in iTunes (more accurately, looking for it; it's not there)

Trying two different CDs in each of the two drives
Doing a repair installation of iTunes

Checking for updated drivers on both optical drives

Opening the CDs in WMP (it works)

Checking preferences (set to "Show CD" on insertion; tried checking and unchecking error correction)

Ran diagnostics; got an "Unable to read audio CD" error message (which, unfortunately, doesn't link to anything useful on Apple's website, nor does anything come up with a search).

Anyone able to make any suggestions?