Do you ever actually save and load the game? Creating a save game object and setting its variable is not enough; you need to save game to slot / load game from slot.
The issue can be related with too many things. You said nothing about how you’re loading and saving, whether is sync or async, if you’re setting the data to be saved in several places, …
Right before you save the object, are you printing its contents, to verify what you’re actually saving?
PS: bump the question for visibility before insulting people who are trying to help you.