Loading an older snapshot, and then loading the previous snapshot.
Also using the “Save” button to save the snapshot, not just creating a new snapshot every time.
The game to save my progress
My entire condo was deleted including a bit of the new stuff i added to my old condo months ago.
If the “Save” button you’re talking about is the one between the ‘Upload’ and ‘My Condo’ buttons, that one is misleading. It doesn’t save a snapshot, but it does force a quicksave (which otherwise happens automatically every 5 minutes or when you leave your condo). It saves your progress for future play sessions, but if you load a snapshot without saving your current condo to a snapshot first, it’ll be lost.
So if you didn’t save a new snapshot (or overwrite one of your existing ones) in the Snapshots menu before you switched to your older snapshot, that’s probably why you lost progress.
I never knew that, why not just have it also save to the current snapshot too? Theres not alot of information about this in the game and I’d expect most people to assume that when they press the “save” button, they are also saving their progress to their snapshot.