It is not just the last achievment.. it happens with multiple story ones.. I already filed a bug report and but a message in the discord channel for this. So I hope they fix it somehow.
If you play in coop only the first one to talk to the npc gets the story achievement the second one does not.
It also affects some single player achievments too which only are possible to achieve as a host.

Hello!
I'm really sorry about this, that sounds really frustrating..

We'll look into this as soon as we can. I think it'd be good to let everyone get these achievements together!

Originally posted by Illyria:

It also affects some single player achievments too which only are possible to achieve as a host.

Do you remember which achievements these are? Just want to make sure we look at them as well!
Thanks,
Jennifer

Originally posted by Inkjet:

We'll look into this as soon as we can. I think it'd be good to let everyone get these achievements together!

It would be better if all of the main storyline related achievements can be obtained by all of the players in the same game, since the storyline is not repeatable.

I am just wondering, will the achivement I missed be marked as completed in the future when you fix the issue?

Originally posted by Inkjet:

Hello!

Do you remember which achievements these are? Just want to make sure we look at them as well!
Thanks,
Jennifer

I made a list over on discord an submitted an ingame bug report as well. Here the list of single player achievements (not story related) which only were unlocking for the host in our playthrough:

Desperate Times, Desperate Measures
Umbrella Farmer
An Aquired Taste
Technically Known as "Water"

Hmm, okay. I'll note these down to look into as well. Thank you!

Originally posted by Inkjet:

Hmm, okay. I'll note these down to look into as well. Thank you!

Any update on this?

Hi again!
We are currently investigating the achievements - those "single-player achievements" seem to be bugged. They should unlock for every player who completes the tasks, but are currently only unlocking for the host.

The story-related achievements, on the other hand, will require some work to allow them to unlock for client players in multiplayer. We're not sure the best way to do this at the moment, but I understand how important it is!

Thank you so much for your patience while we work to squash these bugs,
Jennifer

Originally posted by Inkjet:

Hi again!
We are currently investigating the achievements - those "single-player achievements" seem to be bugged. They should unlock for every player who completes the tasks, but are currently only unlocking for the host.

The story-related achievements, on the other hand, will require some work to allow them to unlock for client players in multiplayer. We're not sure the best way to do this at the moment, but I understand how important it is!

Thank you so much for your patience while we work to squash these bugs,
Jennifer

Hi Jennifer,

Is there any update on this one? I understand you are currently working really hard on fixing all the issues and problems the players submitted, and I really appreciate that. However, in my opinion, for this specific achievement (or others that are similar to this one), it can be very straightforward fix to do a simple check on whether the player is finished the last main quest (or related quests) in their quest list .

For this achievement (New Life - Plant a new Tree of Life), in the situation that multi players are in the same game, apparently it is not reasonable that only the one who picks the final items up and return to the tree will get the achievement.

Please help to escalate this case to your engineer team and I really appreciate it.

Thanks,
Hexor_GT

We have fixed several cases of achievements not unlocking for client players in multiplayer:
“Umbrella Farmer”, “An Acquired Taste”, “Technically Known As ‘Water’”, and “Desperate Times, Desperate Measures.”

For the Tree of Life achievement, I will make sure this is logged and see what we can do.

Thanks so much for bringing this up to me again!

I have to bring this back to top because when I tried to get in the game, it still doesn't provide the achievement for me...

Originally posted by Inkjet:

We have fixed several cases of achievements not unlocking for client players in multiplayer:
“Umbrella Farmer”, “An Acquired Taste”, “Technically Known As ‘Water’”, and “Desperate Times, Desperate Measures.”

For the Tree of Life achievement, I will make sure this is logged and see what we can do.

Thanks so much for bringing this up to me again!

And it's already November...