I bought this game on itch.io when it first came out, and I've done some of the DLC content, but when discussing it with a friend, I was hoping I could look back on it only to find I no longer have the option to point at the announcer and my DLC saves are giving me errors ;n;
Hmmm! I googled the error message and it's telling me that it may have something to do with incompatible save data between devices? I'm really not sure why this would be affecting you though since an itchio version of the game wouldn't use cloud saving like steam might.
I'm very sorry I can't be more helpful, I've never seen this particular error before ^^;
If you'd like to look into it more yourself, a good search term would be "Renpy ImportError No module named Revertable" <- that's the name of the program the game was made in and then the name of the error message