100% my own fault, leaving my comment here for anyone experiencing the same thing, but removing the mention of "bug" as this was absolutely not your fault, incredible mod!!
I had a game that bugged and followed some steps online that solved the issue, but had me tempering with my token and persistent file in AppData Roaming. This made the achievement not save properly to the persistent file, thank you for mentioning it!
Solution for other dumb dumbs like me:
- Go to User > AppData > Roaming > RenPy
- delete your Persistent folder (make a copy if you want - i have only a handful of RenPy games, I didn't)
- delete your Token folder (same)
- Restart the game and enjoy!