They never gave a reason. That said, I felt like the interview with my potential team mates (one of the 3 interview rounds that day) really did not go as well as I would have liked. I could have done better describing my current work and projects. We did some whiteboard design question and ran out of time, looking back I could have done a lot better on that had I put more thought into it. I'm not bitter or anything, it was not my best in person interview by a long shot.