Hey, what do you mean by "not working"? When you install a data pack, you place it in a folder in /.minecraft/saves/[​world name]/datapacks. If the world is already running, you then reload it by doing /reload and then /datapack list to see which data packs are associated with the world (and which are enabled; data packs can be enabled using /datapack enable <name>).

1. If you mean that the data pack doesn't show up in this list, first make sure that it's in the correct folder. Then, if it's zipped (or even if it isn't), make sure it isn't buried in a containing folder (inside the datapacks folder, your data pack should be in a folder, and inside that folder should be the contents of the data pack, which are usually a folder called data, a very important file called pack.mcmeta, and possibly a pack.png). If the data pack is instead inside another folder with the same or a similar name, simply pull it out of that folder and place it in the datapacks folder associated with the world you want to use it with. If the data pack is missing pack.mcmeta, Minecraft won't recognize it as a data pack until this file is added. pack.mcmeta is a file with the following format (for Minecraft 1.20):
   {
"pack": {
"pack_format": 15,
"description": "[pack description (brackets not necessary)]"
}
}If your data pack is missing this file, you can make a new text document, paste this text into it, and change its name to pack.mcmeta (changing the file type is okay here since .mcmeta .txt are encoded in the same way. Minecraft should now recognize the data pack upon a /reload.
2. If you mean that Minecraft is warning you that the data pack is meant for the wrong version, the pack_format field may have the wrong number. Even if you don't change this number, if the data pack is indeed formatted for Minecraft 1.20, it should still work. Changing the number to 15 should remove this warning.
3. If the data pack is enabled but doesn't appear to be doing anything, it depends what the data pack is meant to do. If the data pack alters world generation (e.g. adds structures, custom biomes, or something else when the world is generated), it needs to be added when the world is made. This can be done via a tab at the top of the screen during world creation called More, which contains an option called Data Packs. If the data pack doesn't add anything in world generation (e.g. it adds crafting recipes, advancements, or some other feature), this probably isn't your problem. If you're using a data pack that has some complex mechanic with special interfaces, make sure you've read any documentation (description, etc.) correctly. If you're using a data pack that lets you do additional things using commands, you might need to have cheats enabled or be opped in order to use the data pack.

As other commenters have said, please provide more information. Specifically:

• What data pack(s) are you trying to use?
  
• What sort of error message(s) do the logs contain, if any?
• What do you mean by "not working"? What goes wrong?
• Are you running a singleplayer or LAN world, or are you trying to host a server? Are you using a hosting service like Aternos?

This information will make it easier to help you figure out how to fix the problem.

It doesn't have to be fabric. I play forage and seems to work fine for me