Since 24w09a, commands that set the NBT data of item stacks no longer work as expected.
MC-269037
Commands with item NBT data no longer work
Resolved
Works As Intended
0
In 24w09a, item stack NBT data has been replaced with item components, which use a different syntax than before. The curly braces are now only used to set custom data that can be used by the game but is ignored by the game. For this reason, all previous commands with item data will no longer work, but not give an error message.
If you want to learn more about the new item components, check out the 24w09a changelog: https://www.minecraft.net/en-us/article/minecraft-snapshot-24w09a