Law 14 is here
Once the referee has signalled for a penalty kick to be taken, the kick must be taken; if it is not taken the referee may take disciplinary action before signalling again for the kick to be taken.
If, before the ball is in play, one of the following occurs:
the player taking the penalty kick or a team-mate offends:
if the ball enters the goal, the kick is retaken
if the ball does not enter the goal, the referee stops play and restarts with an indirect free kick
the goalkeeper or a team-mate offends:
if the ball enters the goal, a goal is awarded
if the ball does not enter the goal, the kick is retaken; the goalkeeper is cautioned if responsible for the offence
player of both teams offends the Laws of the Game,
the kick is retaken
So as both Man City players and West ham players encroached (however marginally) on the 2nd (retaken) penalty it should, ridiculous as it may be, according to their own Law and procedure, have once again been retaken.
As for last nights one I have no idea how or why that escaped practically every media outlets attention.