I have an external drive that has the above problem. So: no disk in drive, drive unplugged: I gently tapped the drive on the desk with the opening DOWN about five times. Then I dragged a SMALL nail just past the opening to try and pull out anything that may have been dislodged. Nothing came out. So I did it again. Still nothing came out. So I popped a disc in that I didn't care about into the drive and BINGO... It accepted it!
Hope this helps someone. - Lindy
PS: Hope this didn’t enter twice as I had to sign up before I could comment ;-)