When a data pack is added to a world/already loaded, if the world/server is restarted, most data pack features will not work again until /reload is issued.
How to reproduce (single player):
Enter a world and have a data pack added if none are added (for example, I'm using
which just runs a action bar title command.
Add the pack to the data pack world folder and run the /reload command (Notice no errors in game output, and the actionbar text says "Working" in black text.
Leave the world and come back, the text will disappear after a moment because the command is no longer running.
Type /reload again (shouldn't have to) to see the text pop up again.
How to reproduce (server world):
Load world and join server
Add data pack to world folder in the datapack folder and run the reload command
Notice black "Welcome" text above hotbar (means data pack is working)
Restart the server and rejoin, wait for text to go away
Type /reload again (shouldn't have to) to see the text pop up again.
Ooo someone found this was already posted. MC-186478. Didn't know it was just tick so didn't notice that report while searching.