Check if there is only 1 file inside the “advancements” folder inside your world folder.
If you are on Windows press Win + R and paste: %appdata%\.minecraft\saves
This should open File Explorer.
Search and open the folder with your world name.
Then open a folder named “advancements”
If there is MORE THAN ONE file that looks like this: 61699b2d-0c6a-475f-a0f9-65808d0be2d9.json (random characters), that means the world has been launched with multiple accounts. This is an issue because Minecraft does not merge advancements with multiple accounts.
MAJESTiC8
I’ve had this issue when playing on Mac too. A workaround I found is pressing the title bar and resuming the game.
Interesting! No idea why that’s happening
Pretty sure this is intended behaviour as per slicedlime's (Minecraft employee) video
Check if there is only 1 file inside the “advancements” folder inside your world folder.
If you are on Windows press Win + R and paste:
%appdata%\.minecraft\saves
This should open File Explorer.
Search and open the folder with your world name.
Then open a folder named “advancements”
If there is MORE THAN ONE file that looks like this: 61699b2d-0c6a-475f-a0f9-65808d0be2d9.json (random characters), that means the world has been launched with multiple accounts. This is an issue because Minecraft does not merge advancements with multiple accounts.
Can confirm in 25w35a!
I can confirm on 25w32a!