So. It's been quite a while. As the only person who still has access to fix and work the game, when I was told of the issues with Steam Achievements, I was REALLY unsure of how this was happening. There were still records of them being unlocked by other players.
That said, after some digging, I found this to be a bug that was complicated with a simple answer.
I've uploaded a new update to Seduce Me: The Complete Story in the hopes of seeing this bug fixed. Should it still continue, the hammering shall as well. Please, if you had this issue, feel free to see if the achievements sync up and unlock for you! I would suggest starting a new game just to see if they sync, but it shouldn't require a full reset playthrough! Thanks! - Michaela