The pack uses features that Resource Packs can't access such as textures swapping based on NBT data, so to make use of this pack you need to Optifine which has Custom Item Textures (CIT) built-in or use Fabric and and use CIT Resewn.

If Mojang added the feature so we can check arbitrary NBT values for an Item and swap item models like that I would swap the pack over in a heart beat but sadly this has been a requested feature for a while but never been implemented.

You can use CIT Resewn it's a standalone fabric mod that adds texture swapping

I get this comment sometimes so i'll probably update the description but here is my little to-do list of fixes and checks:

1) Optifine is required.
2) Place the pack above all other texture packs after selecting in game.
3) Please check that Options -> Video Settings -> Quality, then make sure Custom Items is set to ON.

If you continue to have issues you can contact me directly, hope this helps :)

I'm sorry you're having issues with the pack. It should work on servers as me and my friends use it on a server all the time.

But if it works for you in single play but not multiplayer it could be that the servers texture pack overrides it if it has one. The pack only uses the normal Minecraft variant number that comes with the bucket as NBT data unless the server modifies the data before it is sent?

But this is the first I've seen of this issue. If it's a public server it would be nice to know which one it is! If you have managed to fix this issues it's would be nice to know!