Key fragments
I haven't gotten a key fragment in over 3 weeks. I wasn't recently banned or chat restricted. Nor does it say ineligible to earn. I think it's a bug or something.
2 Comments
The drop rate for key fragments is a curve, not a line. With each fragment you earn, the chance to earn your next one goes down slightly. This number resets roughly every thirty days after you earn your first key fragment.
Note: There's currently a bug which prevents you from earning key fragments if you're playing a champion you don't own. This is unintended, and we're working on a solution.
Key frags are definitely bugged but everyone (including Rioters) will tell you otherwise.
The way the system works, after you've earned a few key shards, you are literally meant to not get a single one no matter how many wins you get until a reset happens next month. Currently, the system is set so the player is supposed to earn roughly 12 key shards, enough to open all your chests if you've gotten them.
Right now though, I've gotten 6 key shards only this month and went a full 2 months before hand of not earning any even though I was winning regularly. Sadly there is 100% no help for this. Even submitting a support ticket will end up useless as the Rioters will reply to you with generic responses on how the key fragment system works. (Personal experience on that.) So right now, the best advice I can offer you is to just keep playing until your key fragments decide they want to exist again.