Which version of Unity do you use? Have you already tried to update?
If you use the same trees as Rick, you have to use Unity’s built-in render pipeline, not the HDRP or URP. If converting the materials in Unity does not work, the assets are incompatible with the render pipeline your project uses.
Im not using same assets pack as Rick since it is not available in Unity Store anymore. I found different tree packs, including the one with HDRP support, but issue is still the same.
And when Im switching back to standart pipline my terrain becomes pink…
I started new project, no HDRP this time. Now my trees have a proper textures, but shadows disappears starting from some distance from camera. Please, help… I cannot proceed with course…