Mafia: Definitive Edition

Good solution, thank you 👍

I had collected 3/5 cars and this achievement still hadn't unlocked. I went into the menu and actually clicked on each postcard. The achievement unlocked as I collected the 4th car. This achievement appears to not be unlocking for a few people, checking the postcards might be important. I hope this helps

***UPDATE***

Here's what I did to get the achievement, if it helps you get this achievement:

1. Delete your save from everywhere.
2. Replay through the entire story as all hidden car postcards will be available by then.
3. Go to Bertone's, select and read postcards one at a time (perhaps not necessary to select or read them one at a time but that's what I did. Do this BEFORE locating any hidden cars.
4. Locate hidden cars. Achievement tracker showed all but one located for me, so locate as many cars as what the tracker shows you to be missing.
5. Achievement hopefully pops.



I located and found hidden cars in the game. I jumped in them all and drove them around, except for the one where the guy charges at you with a weapon after the garage opens. I got killed locating that car as I didn't expect the enemy to be there, and was at low health at the time. I never got to jump in that car or drive it around, though it appeared in my garage. After realizing the achievement never popped (with the counter displaying that I had found all but one car), and only then reading the postcards, I deleted my save from everywhere, and replayed through the story.

After completing the story, I selected free ride, went to Bertone's, picked up and read the postcards one by one. Then I located the first hidden car. Upon locating it (with the game telling you which one you found), the achievement popped.

Good luck!