Re: Missing zeta shards from BB8 event

That award is for the Mythic battle which unlocks after you beat tier VII of BB8's legendary event (once you have him at 7*), which you haven't going by the achievement above the one you highlighted, and you stated you have a 6* BB-8.

You might earn this award next time. Beat the legendary event, then beat tier 3 of the freshly unlocked Mythic event (requires 7* BB8 and 4 other strong resistance characters)