The 1.0 release of Valheim changed the save system, so SaveSync for Valheim was not working.
Patch note from Valheim:
New save system: Splits world data across chunks to reduce how much data is serialized and written to improve performance, and is designed to be resilient against mid-write failures
We've fixed this issue. The only catch is that you'll need to do a quick migration:
If the save was never activated (i.e. it doesn't show up in Valheim), click Activate on it in SaveSync once first. Otherwise, skip this step.
Remove the old Valheim save from SaveSync.
Launch Valheim so it converts your local world to the new format.
Add that save back to SaveSync.
Re-share it with your friends.
Valhiem Guide: View game pagehttps://www.savesync.games/
View game page