It is not a matter of fixing as nothing is broken. At the moment,the questline (or at least the possibility of completing it) and the achievement are not available on newer worlds (i.e. worlds that opened after the event originally started).
It is not a bug, it's a feature .
That last sentence is one of most hated in RL tbh, but, as you can see a lot of complaints about "feature" and fix shouldn't be that hard to achieve, and make customers happy. Also, you can see there are a few solutions that can be made, either let us click like we used(previous events) to get cards or add quest items in the shop to be possible to purchase them for bonds. I think we don't ask that much.
EDIT: we have Cards in the shop.