When you place a parlay and one (or more) of the selections in your parlay is a push / no action, the parlay drops down to the next possible number of teams.
For example, if you have a 4-team parlay with three winning selections and one push, it becomes a 3-teamer, with the payout adjusted accordingly. If this happened on a 2-team parlay (one winner and one push), it would just become a straight bet.
With teasers it works similar, however, you can't have a 1-team teaser, so if a push results in the teaser dropping to one team, the entire bet would have no action.
Also, Special Teasers (10 points for football / 8 points for basketball) do not allow the number of teams to be reduced at all, so on those, any push + win will result in the entire bet pushing.