Push gray button in with retracted ballpoint pen tip, grasp middle of CF card with small vise grip pliers or needle nose and firmly pull
straight out. Had this happen once couple of years ago. GL!
Twist it like you are opening the door, and then pry it open with fingernails, pencil/pen, knife, etc. I had this happen the other day (first time ever) and it seemed like the spring just got stuck or something. Hasn't done it since.