Thank you so much for that suggestion! I took it a step further and un/re-installed both Galaxy and the game, loaded up a save and replayed a bit, and the achievements unlocked this time. Problem solved. It also reminded me that I recently did a System Restore that could have messed with Galaxy, so possibly it could have been that if not dropped internet.

In any case, cheers to you! :)

You're welcome, I'm glad you were able to solve the problem!

From your comment it seemed like he had to restart the game from the beginning tho O_o
It's good if reinstalling Galaxy + game was enough (still a pain however)

After the expected 5-week waiting time, I just received this response regarding Deus Ex GOTY / Revision being completely broken:
We are aware of the issue and we are currently in contact with the developers of the game regarding the fix. I am, however, unable to provide an exact ETA. -- ponczo_

I have asked for the hitman's money back.

What will happen to all the achievements I got in the game when hitman is removed from my account? Will remain? Will they disappear?

I reported my problem with this game in December last year, it's here in this thread. I'll write again to see if this helps you:

UPDATE 1 - Mark of the Ninja: Remastered, is a game with constant failures in achievements, and this problem is present on all platforms. In my case, I finish the game, but during the course a series of achievements in history were not unlocked. I am leaving a link below a topic created on the "Trueachievements" website, where several Xbox players report on the problem, and this has been going on for a few years. Apparently I will have to delete my file and save to try again. At least this problem is not exclusive to us.

Apparently the problem occurs in two ways: if you are offline or if the game crashes after completing a level. This causes some achievements to be broken. In my case, at least five times my game crashed after winning a level and the game closed alone.

https://www.trueachievements.com/forum/viewthread.aspx?tid=1055597


UPDATE 2 - I just got 100%, so I can confirm that, in case any achievement breaks, just uninstall the game, delete the saves and restart a new file. Yes, it can end up being frustrating, but it is the only way to solve it. At least it works.

Vesper now has Galaxy achievements and can be removed from the list.
I will say that it is good practice to make back-ups of save-files in case something like this happens. For example, just make a back-up copy after completing each level, it will be less frustrating than starting from scratch. :) It is a habit I've kept for decades.

That's a pleasent surprise. I tried contacting the developers about the missing achievements but I never heard back. The store page still doesn't list Achievements in the list of features, but they can be seen with the old URL trick:
https://www.gog.com/u/YOUR USERNAME/game/1833504782

Although there is no ETA this response is better than I expected, maybe you could try to talk to the Revision guys to see if they have any idea what is going on.

They will almost certainly disappear, if you no longer have the game there is no way to see them.

I had contacted them as well and they promised to add them, even if they didn't have an ETA. I'm very glad they were able to do that.

I was wondering if anyone tried contacting the developers of Recompile about the missing achievements? I did so about a month and a half ago and never heard back.

I'll pass. I don't imagine their response would be any different than GOG's. I had no issue with any of the achievements in Prey Deluxe Edition.

I also tried to ask but they never answered me. They must be the kind of developers who don't give a damn about their customers, at least the ones who buy the game on GOG.

Hopefully they can fix it before the next ice age.

Thanks, I'll consider it fixed and remove it from the list then.

--

I contacted the developers of Rad Rodgers Radical Edition, and since the achievements pretty much never worked, they decided to nuke them.

That's a shame. Thank you for letting me know they weren't ignoring me in particular! I'll keep Recompile on my wishlist at least for now, but it just went way down in priority.
On the one hand, I'm not very optimistic that Deus Ex Revision will be fixed because apparently the issues cropped up with GOG Galaxy 2.0, so nearly 2 and 1/2 years ago. On the other hand, Gemini Rue was released in 2011 and it just got an update a few days ago, so who knows.
Incredible. They also left "Achievements" under game features on the store page.

A number of achievements are broken for Real Heroes: Firefighter HD, both here and on Steam:
Berserker
Can Jockey
Dragon Slayer
On a Roll
Smoke Eater
Super Soaker

Thank you, if they haven't been fixed on Steam either, it's unlikely they'll do so on GOG, but hopefully sooner rather than later they'll release a patch that fixes the problem for both versions.