Retake the penalty kick
The referee demanded the penalty to be retaken because the goalkeeper anticipated where the ball would go.
The reason, probably, was because he stepped off his line in the process, breaking the penalty kick rules.
Until around about the early eighties, the goalkeeper could not move before the ball was kicked, but FIFA realised in the modern game this is impossible to administer. The rule, since then, is that the goalkeeper can move before the kick, but cannot move off the line.