my first thought is this matches the behavior resulting from backend editing of files that circumvents some ren'py games not reading edited saves.
One of the big consequences of that is breaking persistent values, such as what's used to track both "seen dialogue" as well as how we unlock the CGs.
If you don't remember the specifics, go to the AppData\Roaming folder ( so C:\Users\Username\AppData\Roaming\RenPy) and delete the whole folder, going "scorched earth". Your saves are stored in the local game folder, so you shouldn't lose anything, but this should be the last resort if you don't remember what you did otherwise.
It won't unlock the ones you "should" have, (you still would have to replay to get those) but it should allow you to unlock them going forward.