Love always finds a way (on this occasion, it just needs a little help).
While playing Fill the Empty Hearts levels, you'll need to match candies next to the love hearts to move them along the track. Each heart has a dedicated mold it must reach, so be sure to check the line it follows.
Sometimes the line will run under other blockers. This is why you need to clear the path as best you can.
Reunite the heart with it's devoted mold in a limited number of moves or you'll need to tackle the level again!