After searching for so many answers to this question, I found the solution for me:
I had an old save file format that was making my save game load fail. I just deleted it and everything is fine.
The symptoms of the problem were:
- In the Unreal PIE mode, save games worked fine
- In the Unreal Windows packaged build, Save Game to Slot and Load Game from Slot didn’t work
My solution:
- Open Windows explorer
- Show hidden items (View menu > Show > Hidden items)
- Navigate to C:\Users<your user>\AppData\Local<your app name>\Saved\SaveGames
- Delete old save games
What I think was happening:
- I created an old save game format and there was a save game file there
- I recently made a new Save Game blueprint (BP_SaveGame), but the Variables didn’t match
- When I tried to load a save game from slot, that actually worked, but the Cast to BP_SaveGame failed
- Deleting the old save game file lets Unreal regenerate the file in the correct format
