Chest not resetting in the new season?

CHAMPION MASTERY

Every ranked season, you can earn one free Hextech chest per champion. If you or a premade ally get an S- or better grade—and you haven’t already gotten a chest for the champ you were playing—you get a chest! Score big across a wide variety of champs and you can earn up to 52 free chests per year.

With the start of the 2017 ranked season, you’ll be able to re-earn your one free Hextech chest per champion. http://na.leagueoflegends.com/en/featured/preseason-2017/gameplay

Well I still can't get boxes from champ i got chest last year.