tree problems

ok so im a little new to unity and well i made a mushrrom in c4d and imported it into unity as an asset and i wanted to use it as a tree for this trippy scene im trying to make but unlike the premade palm tree and stuff it wont work when i use the tree paint tool on the terrain tab. it keeps saying invalid prefab.

can someone help me solve this problem

Do you got valid mash render?
I sugest you to make another prefab
Go asseets-new-prefab
import the thingy there and make a valid mesh render.
Ok ty for reading

ok ill try it out thankz a bunch