No Chest after getting S-

I played a game as Teemo and got an S- that same game. I have a chest available as well and I have yet to get a chest on Teemo this season. Any clue as to why I didn't earn a chest? Note: The game gave me a Mastery 6 token after the game since it was my first S- on Teemo, so I don't know if that trigger could have caused a problem. Edit: To clarify I'm honor level 3, never been banned, I have chests available and again, I have not gotten Teemo's chest this season, and the same thing just happened again as I got an S with Singed and no chest even though I clearly have one available. So what's going on?
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