12 days ago - AndrewT - Direct link
Steam cloud saves can be seen here:
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If yours are not there, that basically has to be a Steam issue. Click on this game in your Steam Library, what does it say about cloud sync status there?  
9 days ago - AndrewT - Direct link
Do your cloud saves appear on that Steam page? Or not?  
8 days ago - AndrewT - Direct link
Is this only with CK3? What if you do cloud saves with EU4, Stellaris, or CK2?

And has this always been the case with this game? Or it was okay up to some point?

You could try a Steam Flush Config
support.steampowered.com

Steam Support :: Clear download cache

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