Save Volume Slider Settings To Save Game Slot?

Similar questions have been asked on here, but none of the answers seem to work for me so I’m posting a new one here with screenshots.

I have an options menu for graphics and now volume settings. There are 3 sliders for master, music and SFX, which I’ve set up classes for. The sliders work fine when tested on their own (as per the second and third sliders below). However, when I try to save the values to the savegame slot (as per the first slider) it just resets back to default values when I exit/reopen the game. Not sure where I’m going wrong!

Edit: The gamegame blueprint is ‘SaveGame_Settings’. It has a string variable for ‘MasterVolume’, ‘MusicVolume’ and ‘SFXVolume’. I have the same variables stored in my game instance blueprint and in the settings menu widget blueprint (screenshots below).

Well, you’re casting nothing, and you haven’t specified a save slot:

344185-screenshot-1.jpg

Here’s a save game 101: