Okay, League

So, can someone explain to me what's going on with Hextech Chests?

I have had a lot of issues with this for a while. For instance, I got Leblanc finally to level 5 and...: no chest. I got an S- on Ashe!: no chest. I got an S on all manner of champs, but no chests!! I have no idea what it's doing. I hope this is some sort of horrible mistake. It's been going on for a while now, maybe a month or two? S's are hard to get and level 5's happen only once, so I feel I little short suited (i know, distress of the privilege and all that, but if I'm promised something for hard work, I should get it shouldn't I?). And it's not because I'm out of "available chests", no: I have all 5 available. So I have no clue what's going on, but I've missed out on two if not more hex tech chests (probably more). I have no idea what's going on with it so I just want to bring in to the attention of someone (who might have an answer). Please, do let me know!

P.S. I'm adding a poll just in case this is happening to you guys, too.