unfair play


Your opponent is premium and premium members get placed on vacation automatically when low on time in one or more of their games, with the exception of games in no-vacation tourneys.
Your opponent will eventually come off vacation and move.

yeah your opponent is probably afk for a while maybe due to work or an actual holiday, when they go on vacation during a game but continue to log in and out of chess.com is when it gets annoying.

The status change to on vacation means he is on vacation, actually easy to understand. If he is on a real vacation or just busy or lost the fun to play with you, no one except him knows.
Your information u give us is wrong, the status change must have been before expiry. With change to on vacation the possible 14 day-expiration is disabled, until he is back.
Hope this helps you!