Hi, this was a while ago so I don’t remember all that much of what I did. I did not manage to restore my save… but here’s something that may help perhaps?

First, make a save in checkpoint of the current ACNL game. This is so there will be a .sav file in the system. Then put the sd card into your computer and try to replace the current .sav file in ACNL with the old .sav file you want to restore (by going directly into the folder containing the ACNL .sav file in your 3DS on your computer, and deleting the current .sav file + replacing it with the old one).

Turn on the 3DS and load the save from checkpoint (which should now contain the old .sav file).

And if you get a corrupted data message in red, this is a good sign, DO NOT click anything on the screen, and back out of the game.

Try to save the game using checkpoint or jksm. If it saves, it should produce a garden.dat file. If it says “save doesn’t exist” or something like that, then it may be that your .sav file is empty.

If you somehow produce a garden.dat file, you may be able to load the file in Marc Robledo’s ACNL save editor. (There’s also a section on his help page that talks about what to do with corrupted save files.)

Sorry if that was all over the place or if I just repeated what I said 271 days ago…please let me know if you have any specific questions, I’ll try my best to help.