CK II - 3.3.0 (PILA) User modification impacting checksum- no mods used ever

[Kinjion]

One line summary of your issue
3.3.0 (PILA) User modification impacting checksum- no mods used ever

Game Version
3.3.0

What expansions do you have installed?
Jade Dragon,
Monks & Mystics,
The Reapers Due,
Conclave,
Horse Lords,
Way of Life,
Charlemagne,
Rajas of India,
Sons of Abraham,
The Old Gods,
The Republic,
Legacy of Rome,
Sword of Islam,
Holy Fury, All of the above

Do you have mods enabled?
No

Please explain your issue is in as much detail as possible.
I can't unlock achievements or earn credits on Monarch's Journey because I have the "No user modifications that change the game's checksum" message disabling them. I have never used a mod. I've tried starting a new game, uninstalling and reinstalling CK2, turning off all my DLCs, and validating my game files. Nothing works. I haven't been able to unlock any achievements for months. Now that I can't do Monarch's Journey either I'm beyond pissed.

Steps to reproduce the issue.
Load my game and try to do anything with achievments, I guess. It's a problem in every iteration. And yes ironman is on.

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[Aardvark Bellay]

uninstalling and reinstalling CK2

Manually delete the folder before reinstalling.
Autouninstall leaves the folder behind and might also leave files in there.

 

[Aerotinge]

Steam validate game files that existed and required. But it won't check if there's extra files if any, which change checksum for sure.