Unable to play songs purchased from iTunes on an Authorized computer.

I have purchased music from iTunes and when I go to listen to them on an Authorized computer, I keep getting a pop up saying I need to type in UID and PW because it isn't authorized, when info is typed in, computer advises that this computer is already authorized, click ok, and attempt play song again, and get the exact same pop up. de-aurthorize computer, log out of iTunes, restart computer, sign into itunes, reauthorize computer, and attempt to play song and get the same error... cannot play music that I have purchased no matter what I do. I have signed in/out of itunes, restart computer several times, still no go. this is on a macbook pro, iTunes and all other apple software is up to date, and I have 3 of 5 computers authorized for use, and the song does appear under my purchases for my itunes account info. Totally at a lost at this point, have music I have paid for and cannot play them no matter what solution I try from the discussions.