cccsdad,
The MLB Umpires Manual says: "On a play at the plate, should the runner miss home plate and the fielder miss the tag on the runner, it is preferable that the umpire make no signal on the play.
At first base, the accepted mechanic is to signal safe if the B/R passes first before the ball reaches the fielder.
I don't know the accepted mechanic if it is a force play at the plate.