As a rule of thumb for Ren'Py always start with a fresh game.Same for me but when i wanted to play this patch i couldn't even start the game without getting an error. After deleting everything game related, even save games, and unzipping it new i can play completly fine without any error.
And if the saves are not stored in two places as it is on Windows, them copy the saves.
But if you are on Windows then always delete the previous game an start anew. The saves are stored on AppData too. So if you don't see your saves then that means that they are not compatible. That way you will save you a good deal of issues.