I'm Not Getting ANY Key Shards

They reset every month. Whenever the last time you got one was, you won't get them again till that time in the next month.

Whenever you get a key fragment, the drop rate for the next key fragment is lowered, and this continues every time you get a key fragment. The drop rate resets approximately 1 month after you have gotten your first key fragment at the original drop rate.

Also, you can raise your chance at getting one by queuing with a premade.