In-Game Secrets won't sync with Steam Achievements?

[1# Crazy Frog Fan]

I have three achievements that are not unlocked in my save file, I tried to sync them by going to the stats/secrets menu and pressing ALT+F2 but the secrets won't unlock.

[Nazemec]

Originally posted by 1# Crazy Frog Fan:

I tried to sync them by going to the stats/secrets menu

This unlocks Steam achievements based on your in-game secrets, not the other way around.

Originally posted by 1# Crazy Frog Fan:

and pressing ALT+F2 but the secrets won't unlock.

This should work though, assuming you press it while in the stats menu.
Note that it will only unlock the secret in the secrets menu (meaning it can be generated during runs), it doesn't show corresponding completion marks or cross out challenges.