The new Iceborne expansion for Monster Hunter: World launched on PC yesterday. For players who are running the new campaign without issue, RPS' Iceborne review calls it one of the "bestest bests." For others, save file issues and performance problems might make for a frigid first experience. Make sure to back up your MH:W save files because there's a chance Iceborne or the simultaneous game update could delete them.
As spotted by VG24/7, some players who jumped in to the new Iceborne expansion have noticed a message when they load in saying that "no compatible save was found." If you allow it, players are reporting that MH:W will start a new save file, immediately replacing and deleting your old data, including your Steam Cloud save.
There are threads related to the issue on Reddit and Steam but it's difficult to say just how many players are affected. One thing is for sure, if MH:W notifies you that you don't have a compatible save file, decline to create a new one. You still may be able to manually back up your files. You can find your save data in:
Program Files (x86)\Steam\userdata\[Your Steam ID]\582010\remote
As a note to those with multiple drives: I found my save file data located in the Steam folder on my C drive where Steam is installed, not the larger drive where my games are installed.
[PC/Steam] We are aware of performance issues that have been reported, and are currently investigating them.— Monster Hunter (@monsterhunter) January 10, 2020
If you have been experiencing any issues with the PC version, please contact Capcom Support and be ready to share more info on your system: https://t.co/qf4EFm6HJK
The official Monster Hunter account on Twitter has acknowledged performance issues, but has not mentioned save file loss, so the exact cause is still unknown. Capcom have reportedly told Polygon that they are "aware and are looking into the issue."
Some players have theorized that the save file losses are caused by a previous update to MH:W's save file format. If you haven't played World in some time, jumping straight to Iceborne, which does not recognize the old save format, might cause keep the game from recognizing your save data. One way you may be able to avoid the issue is by starting up MH:W without Iceborne installed, forcing the game to convert your save file, before jumping into the expansion.
If you don't have the Iceborne expansion yet, you can find it on Steam for £35/€40/$40. If you've already begun Iceborne and are having trouble with its monsters rather than its performance, check out our guides for defeating the Banbaro, Barioth, and all the other icy creatures.