From what I can see in the pictures the grower planted the tree too deep. It appears as if a part of the graft is in the soil. I cannot see the root flare and this is very important. Remove enough soil from the top to be able to see where the roots begin if you can't see them now.
I don't have much experience with growing these other then a few failed attempts at trying to grow one from a store bought avocado which finally succeeded after rigorous bleeching in order to cut back molds. To me this looks like major transplant shock though and less to do with what you are growing and more so the techniques applied. I could be wrong here but that stake seems to have been jammed into the ground after the transplant into the root system causing major drooping. Also could be a graft in which the cloning process might need some work. Did you start with a root ball? Chucks more in your zone, temps could be a thing too.