s/he decided s/he doesn't want to play the game anymore. you can abort the game within the first two moves without it affecting your rating. your recourse is start a new game and not think much why the other person decided not to play. 
Aborted Game
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I'm new to Chess.com and tried to play a live game. As soon as we were connected my opponent aborted the game. Why would he/she do that and what is my recourse?