The datapack isn't working, when i use /datapack list it says, that it is loaded, but it doesn't work.

I found that if you click the "Data Packs" button on the World Creation Screen, only then will the datapacks actually work.

Fixed in v1.14

Fabric, Forge or Quilt? Also what mod and game versions are you using?
Additionally, could you provide me the datapack if possible?
The ones I am using for testing seem to work without issues.

The mod version i used is: global_packs-fabric-1.19-1.13_fabric
I tried it with Terralith and WWOO. (i didn't load both at the same time. They are incompatible)
https://www.planetminecraft.com/data-pack/terralith-overworld-evolved-100-biomes-caves-and-more/
https://www.planetminecraft.com/data-pack/william-wythers-overhauled-overworld/