Can't unlock rock bottom

[KechaVais]

I've beaten boss rush in easy and hard mode, got the achievement, the completion mark shows but I used the seed (HSHF NKX4) that has the item but it doesn't appear.

[Nazemec]

If the seed was generated before the latest Repentance content update it is no longer reliable.
Same goes if you have any modded item installed.

Just check the secrets menu, number 433. If it is visible, then the item is unlocked, no doubt possible.

[KechaVais]

Yes, the item appears in 433. Well, i'll wait for the item to show up, idk. Thanks!

[yanglin751115]

I have the same problem, after beaten boss rush using Jacob and Esau, the game just did't show the icon of secret unlocked and neither steam showed achievement unlocked. But I can see the completion mark shows and secrets number 433 unlocked.

I still can not see any bottom rock showed up after a long time playing, I'm not sure whether I'm just bad luck. I have tried to craft rock bottom using tainted Cain but can only got other random items.