We released achievements yesterday, but it's been brought to our attention that not enough of them were retroactive.
We're pushing a small update today (0.9.4a) which should have almost all achievements be retroactive upon loading a save file.
If one of them isn't retroactive, feel free to drop us a line on the forums, but chances are that it's normal, as there are a very small amount that aren't retroactive. There 8 (out of 43) non-retroactive achievements, including 6 "in-combat achievements", 1 trivial-to-unlock, and 1 crafting related.
That's the only change for the new build, so no patch notes this time!
Let us know how it goes!