Hmm, that could happen if you did not place the folder correctly, you should follow the guide on the first page.
Have you made sure that you did one of the following:
A:
Just place the content of the zipfile in its entirety on any drive location and double click the LuosFreeCaves.uproject
Now it should also show up on the launcher.
B:
Copy the “Content” folder into your project folder (you should see a “Content Folder” already.
It should not overwrite anything. (DONT do this if you already own the purchasable package, as it already contains these assets)
C:
Place the content inside the “Content” folder in the “Content” folder of your project.
Because not doing so will break the material function location, as well as the texture locations, and the material will not be able to find em.
__
I just downloaded 4.22 and a fresh version of the free cave pack and it worked fine for me.