If your game is on patch v1.573.834 but your save is for v1.687.302 , it is unlikely to work.
: These saves are specifically placed in local directories (usually C:\Users\Public\Documents\Steam\CODEX\1551360 ). save game forza horizon 5 codex best
Navigate to the following path: C:\Users\Public\Documents\Steam\CODEX\1551360\remote If your game is on patch v1