Hextech Chests

I don't get Hextech chests at all. I checked before playing a game that I never got a Hextech chest with Ashe, I played and 3 of my teammates got S ranks but I didn't get a chest and when I checked, it said I got a chest with Ashe. In addition to that, the "Chests Available" are always all used up, light yellow colored. It says I used all of them and it doesn't tell me when is my next chest gonna be. Is this a glitch? Why don't I receive Hextech Chests and why does it say I already got 4 of them even though I haven't in months! Please respond asap.