Ensure the save file matches your game version. Some updates may cause older save files to become incompatible. name for your local installation?
For the CODEX/FitGirl version, the save files are not located in the standard Steam directory. You must navigate to: How to Install forza horizon 5 codex save game 100 link
Paste the downloaded files into the directories listed above. Manage User IDs: Ensure the save file matches your game version