First and foremost, are you running Grove v0.308?
Have you properly extracted / unzipped the game? If you haven't done so, your saves won't write.
Additionally, have you made sure to save your game to a location on your harddrive? Saving to cloudsync options like OneDrive or iCloud causes discrepancies that can make saves disappear.
If the problem isn't any of these things, then we'll need to see a screenshot of your save folder to determine more details.