[PLUGIN] Savior

Hello,
Just have a strange behaviour.
For my game, I save and load data using save level and load level function. Everything is ok.
For a specific reason, I need to save separate variable to be “independent” from the level saved and loaded. These are variables that must not be saved in the user slot, because contains variable that has to be valid whichever slot I decide to load (i.e. overall game time)
To do this, I put this variable in the custom game instance of the game. I tried to create a specific slot and trying to save with the save game instance function, but no file is created. The function is run from the game instance itself.
In the specific savior 3 slot, I added as the object scope the custom game instance. Only this, but it doesn’t save anything.
Any idea in regards to what I did it wrong?

UE4 version is 4.25.4.