Ravinius: I know that it was already reported throughout the years, but for me it's a slightly different set of achievements. People were reporting the ones about destroying certain numbers of fighters and capital ships. I have problem with the most basic ones:
on the go- trade with a merchant while in flight
under the table- succesfuly bribe a militia officer
I did both of those things and the achievemnts didn't pop up. Additionaly the one ahievement that I did manage to unlock sweet new ride for buying a new ship did pop up in game but not on galaxy (initialy). I had to leave the game, start it again, buy the initial ship and only then the achievement appeared on galaxy. The one fix that other threads mention- launching the game through play button in GoG Galaxy doesn't work for me (I always launch this game through the client precisely for achievements).
Some fix would be appreciated but if there's none then it's not a terrible deal breaker as the game is rather to my liking and I'm enyoing it massively.

Ravinius: The problem is I have overlay turned on by default. Also since my initial post I managed to unlock on the go achievement (but at first I only got the gog galaxy prompt while in game, it unlocked on my profile a few minutes later).

Det_Bullock: The game detects achievements only when played through Galaxy with the overlay on, if you don't any achievement for stuff you have already done won't unlock and you'll have to start the game over or load a save from before you've reached the related milestone.