Some of those who jumped into Monster Hunter World: Iceborne immediately after its release found that their save files are gone.
Monster Hunter World: Iceborne released on PC last night. Although the launch has been relatively smooth so far, some players ran into a major problem.
Upon starting the game, Monster Hunter World does a save file check. When this happens, some players received an error message letting them know that "no compatible save was found." If you continue along, the game will create a new save file, immediately deleting the old.
If you have cloud saves enabled for Monster Hunter World, the new save will replace the existing one in the cloud as soon as you exit the game. This caught many off guard, and it's not immediately clear what causes it.
Some believe it has to do with mods, many of which are out of date at this point. Others think the error occurs if you haven't played Monster Hunter World in a while, which means you missed out on a save data format change that took place post launch.
Seeing as the game can't read the old format, it suggest starting over, which obviously isn't ideal.
If you've yet to launch the game since Iceborne's release, you may want to back up your save file locally just in case. Monster Hunter World typically stores those files under Steam\User data\(your steam user ID number)\582010. You should also back up everything in the savedata_backup folder in the game's directory.
Keeping a copy of your original save will help in case you need to do a safe transfer.